The books have been very helpful in where everything goes. I've been able to figure out why some stuff doesn't fit, well because the previous owner probably didn't have these! My only complaint would be: For the price I expected good lines and great diagrams. Instead I find it difficult to read due to the heavy watermark (could have made it more opaque, I took some printing courses its not that hard) and even more difficult when parts of the diagram are actually missing. I am not sure if they are missing on purpose to show like a large gap between the areas but it confuses me alot. Otherwise the pages that are complete have been very helpful!