If you'd like to get some more insight into the mind of late, great music legend John Lennon, you can pick up The John Lennon Letters book for just $20.
The book is comprised of old postcards and letters that Lennon sent to family and friends while he was alive. This is an interesting mental snapshot of Lennon since he did not intend on the public seeing these particular letters. They reveal his relationship with different people, his thoughtfulness and his values in a way we've never seen before.
This John Lennon Letters book is edited and annotated by Hunter Davies, who wrote The Beatles' 1968 authorized biography.
An interesting fact on this book is that it also includes postcards written to total strangers.