Practical Math

Chenier's Practical Math Application Guide is the kind of math I wish they'd taught me in high school. Each section uses real-world situations (with a homebuilding bent) to illustrate different math principles, so you simultaneously learn trigonometry and how to lay out stairs, geometry and how to level with a plumb-bob. It has worksheets to practice what you've learned as well as "trade tricks" for DIYers that you wouldn't find in a math textbook.

Many makers know this stuff intuitively already, but if you're new at this kind of thing, the book is a great resource. By the end, you'll know how to deal with unequal roof pitches, but you might just be a bit more of a math geek, too.