Allen Bedford starts off the book by talking about how well engineered the LEGO system is and why it works together so well. He not only goes over the basic classification of each type of piece the reader might come across, but he even goes into detail about the measurements of each piece and why everything fits together so well.
Chapter 2 introduces some basic techniques for combining the bricks, all of which are used extensively in the rest of the book. One is called Stacking. This is where you simply line up the pieces vertically all in a column. While this makes for nice uniform lines, without reinforced layers, these columns of LEGOs can easily fall apart. The second technique is Overlapping, and this technique has the builder keeping track of where each layerís pieces separate and making sure that the layer above and below have a piece crossing over that gap. This can easily be seen when looking at a normal brick wall and seeing how each layer of (non LEGO) bricks are offset from the ones above and below it. The last technique is called Staggered, and this puts the layer away from the front-edge. The result can be a series of steps or even a blocky roof for a house.
This chapter continues showing how to make your models structurally sound by going through the different types of columns and cross braces you can build. Like building walls, there are a few different techniques, and they all pretty much depend on how tall your column will be and how strong or square it needs to stay. The stronger columns will use more pieces, but they are less likely to twist or lose support as you get taller, but at the obvious cost of weight.
From there, The Unofficial LEGO Builder's Guide, 2nd Edition starts talking about the different scale sizes you can build. In fact, the different scales are the subject of the next four chapters. The first is the one most LEGO fans will be the most familiar with, Minifig Scale. This would be the scale that fits best with the minifigs. Bedford shows off this scale by going through the steps to build a small train station.
Next is the Miniland Scale. This was introduced by LEGO when LEGOLand first opened and had scenes of a much larger scale. Instead of using the minifigs to represent the size of a 6 foot tall person, people were built out of a series of other LEGO bricks. The resulting scale is about 2.5 times bigger than Minifig Scale. The book not only goes over how to build various Miniland people, but it also shows off a building facade similar to what you would see on a movie set where only the front and a couple of walls are actually built with a hollow interior.
The book continues by making everything even bigger. Jumbo Scale has you building bigger LEGO pieces out of smaller ones. While there are several scales in this mode (i.e. 4x, 6x, 10x and 12x), the principles are all the same. If you wanted to build a standard 1x1 brick in a larger scale, then you basically need that scaleís worth of bricks. For example, a 1x1 brick on a 4x scale has each side being 4 studs wide. For a 2x1 brick, the dimensions of a 6x version would be 12x6 studs. The height is a little different and thatís because a standard LEGO brick is taller than it is wide, but the general idea should be clear. What I find amusing about the Jumbo Scale is that the book suggests starting off with standard playsets that you would buy in a store, just making your own bigger version of each of the pieces so that you can get a good feel for how the different versions feel compared to the original.
Before moving away from the different scales, The Unofficial LEGO Builderís Guide goes in the opposite direction and talks about the Microscale style of building. Here, the idea is to make your model as small as possible and still supply enough detail to make it obvious what the object is. Bedford shows off a Microscale model of a cargo ship complete with shipping containers (2x1 bricks), but then goes into detail as he builds a Microscale model of the Empire State Building. He also talks about how to replace larger scale parts like wheels and windows with smaller pieces to still convey the purpose of those parts.
Chapter 7 is all about using blocky LEGO bricks to make curves and spheres so you can represent more realistic items. Of course, scale is a factor here as well, but more because the bigger the scale, the smoother you can make a curve. Think of it as trying to draw a circle in a pixel art program like MS Paint. If you zoom in on a small scale, you can see the individual pixels (in this case LEGO blocks) and you can see the jagged curve, but if you zoom out, those jagged curves can appear to be a smooth arch. The book goes over this subject by showing how to build a sphere and a model of The Sphinx, complete with broken nose.
In a similar subject to trying to make curved 3 dimensional objects out of LEGO bricks, this book also covers mosaics and how to use the pieces to represent 2D pictures. The book offers two styles, studs-out and studs-up. The first has you looking down at the pieces from above so that you see the studs and each pixel (for lack of a better term) is a 1x1 stud. The other allows for a bit more detail since you are looking at the side of the plates instead of the top. This means that you can make more gradual changes, but each pixel is no longer a square, they are wider than they are tall. After showing both styles off with mosaics of the word "LEGO," Bedford goes on to show how to sketch out basic repeating patterns on grid paper and then how to take an image that you want to make a mosaic of and drop its resolution so that you can translate the now blocky image into a piece of LEGO art. He does this with a picture of an angelfish and a cat named Izzy.
Chapter 9 is all about using the skills and techniques learned in the earlier sections to build a model from scratch. The focus of this chapter is a space shuttle. Bedford goes through each step from drawing out the shape of the shuttle on grid paper to know how big to make the model and what pieces best fit in the shape drawn out, to building up each layer and explaining what techniques he uses and why he makes the various design decisions he does. As a final chapter about the building process, this example does a pretty good job of showing how everything comes together.
The book also talks about several websites like Brickshelf and My Own Creations Pages that allow hobbyists to share their designs with fellow builders. It also mentions a program called MLCad that lets you build your models virtually with an unlimited supply of pieces and colors.
The Unofficial LEGO Builder's Guide contains two appendices. Appendix A is a fairly indepth list of all of the major LEGO bricks/plates/whatevers you will find yourself working with. The book canít possibly list everything that LEGO has ever put out, but it is a fairly comprehensive list and it does a good job of organizing the different types so that you can easily know and talk about how certain types relate to and are different from other types.
Appendix B talks about using grid paper, a specific type designed to fit the shapes of the LEGO bricks themselves, to draw out rough drafts of your designs before just jumping into a pile of LEGOs and attempting to get all of the scale and details right on your first go.
Like I said above, The Unofficial LEGO Builder's Guide gives the reader a lot of groundwork for building both strong and interesting models. Many of these techniques are derived from real-world examples (like the Overlap technique as seen in real brick walls) and it is all well written, so it doesnít take much to understand the ideas being conveyed. If you have any interest in putting together your own LEGO models, then this book is a good investment.