anyone know any good books/places to read up on how to build guitar cabinets?

Do a google search for "detuned cabinets". These things use 1 port per speaker, with the port area equalling the speaker area. A couple of sites have dimension specs for the cabinets, construction techniques, etc. I use two for my bass, one with 2x10", one with 1x18". Made 'em out of 3/4 plywood and 2x2s. They sound really good. You might think, "Why don't you just fill the other two holes with speakers and get twice the sound?" The sites explain the physics of the concept, so my uneducated self won't try to.All I know is that my 2x10 is louder, and sounds better, than commercially available 4x10 cabinets that I've tried. You can see some pics and hear music samples at my band's myspace page:
www.myspace.com/thetransmissions.

As for construction tips, mine is: measure twice, cut once...

cool, thanks.

My drummer built me a 2x12 cabinet with celestions and built a tube head to go along with it. I was just interested in reading up on it.

Check out this link:

http://www.londonpower.com/speakers.htm

On the page you'll find:
London Power DIY Speaker Cabinets for Musical Instrument Applications, listed on the Power Press Publishing book page with a complete description. $15 US US & Int'l; $19 CDN within Canada.

Get the book, it's great!