I stalled out after a couple hundred pages into the new Schulz biography. As a cartoonist friend of mine said, "It's tough sledding."
If you're looking for a book on Schulz that provides a fuller -- and more enjoyable -- portrait of of the man and his work, track down Good Grief: The Story of Charles M. Schulz by Rheta Grimsley Johnson.
The book was first published in 1989, but is now, sadly, out of print. Used copies can be found here. I got mine (a British edition published by Ravette Books) over 10 years ago.
Ms. Grimsley doesn't shy away from Schulz's gloomier side and does, in fact, deal quite openly with his depression and problems finding -- and accepting -- happiness. She also includes a lot of great anecdotes and quotes from various cartoonists, both old and new.
And for what it's worth, Bill Watterson recommended Rheta's book, too.