"Lance Armstrong's War" is my favorite (though I'd never heard of "23 Days..."). It follows Lance & co. through the 2004 season, but it talks quite a bit about other pro cyclists, Sheryl, Lance's teammates and trainers, etc. It also gives some insight into what the life of a pro rider is like, sprinkled with some very interesting facts and bits you'd never find out about otherwise (the part about the "a$$-check" made me laugh out loud). I recommend it.