I need some picture books that would show how to do various leg exerices that work the quads and ham strings to help stretch them and keep them limber. Apparently, form sitting all day at work, these muscles are quite stiff playing into my back problems.
Any suggestions?
Get a copy of Stretching by Bob Anderson. Pretty much the best book written on stretching and every single stretch is illustrated with an easy to understand drawing.
This site has many animations for various exercises and stretches.
Moving this from IMHO to Cafe Society.
Before you spend your money on picture books, visit your local news stand and scope out some Muscle & Fitness mags. Cheaper. Usually chock full of very well illustrated step by step routines. You’ll find that every other month or so has a leg routine program.
FWIW, I think that the women’s issues (M&F for women) has far better lower body and ab routines than the men’s version. Plus, you’ll save money by not having to buy Maxxim any more. 
There’s a workout/health book featuring diagrams and written instructions for different exercises. It’s either from the “Idiot’s Guide to " series or the "__ for Dummies” series, and it can probably found in your local public library.
You might want to check out Bill Pearl’s Keys to the Inner Universe.