Reddit mentions of David Vizard's How to Build Max-Performance Chevy Small-Blocks on a Budget (Performance How-To)

Start Here. It's a dated book, but the technology behind the 350 hasn't changed much in the last 15 years. So much of the information is still good.

Long story short - tuning a carburetor is dialing in your various jets and needles to match the fuel demands at whichever throttle position. In some cases it's as simple as turning a screw, in others you have to begin swapping jets and pumps. It all depends on the carburetor you're working on.

You should be able to find several books on Amazon, check out this one- http://www.amazon.com/Build-Chevy-Small-Blocks-Budget-Performance/dp/1932494847/ref=sr_1_2?s=books&ie=UTF8&qid=1377614427&sr=1-2&keywords=small+block+chevy
I've read several books from that series and they are very helpful.

This kind of depends on a few things. What kind of car(s)? What kind(s) of engine? One book that helps one enthusiast might be useless to another kind of enthusiast.

Coming from my experience with muscle-era cars, I've found these to be valuable:

Haynes or Chiltons manual for your particular car: Nothing too advanced here, but it gives you most of the general stuff like fluid volumes and, most importantly, torque values for the various fasteners.

Small-block Chevy Engines:

"How to Build Maximum Performance Small Blocks on a Budget" by David Vizard. This was my bible for a while. Tons of straight-forward, no-BS information, engine theory, and data on stock and aftermarket parts and how to get the most out of them. It obviously focuses on SBCs, but lots of the stuff is applicable to other engines, too. The link above goes to the edition I own, this one seems to be the one currently in print.

"How to Rebuild Your Chevy Small Block" is like a Haynes but for the SBC engine: Step-by-step instructions on how to disassemble and reassemble the engine with everything you ever needed to know included, with some performance and money-saving tips along the way.