The book is a concise and chronological account of the life of C.S. Lewis. There is a lot of information to absorb with place names and people, and the like, who may only appear for a page or two - then you're on to the next set. Add to that the random characters who arrive for one random sentence and you have yourself a challenging read, at times.
If you can put all that to one side and focus only on CSL (or Jack, as he preferred to be called) you will find an emotional rollercoaster of a story. Jack was an exceptional man, in more ways than one, and his life story is certainly worth reading about.