The beginning was a little slow for me, I wasn't super interested in his early childhood. However, the book definintely picked up and I got into it. I love his style of writing and he brought me to tears a few times towards the end and overall kept me entertained.
I am on the same page as my sister in the fact that I don't like when my mental image is influenced. I totally ruined the Twilight series for myself when I obsessively read the Stephenie Meyer website during a summer waiting for the next book to come out. After that I could hear her "voice" in her writing and it was no longer my Bella narrating her love story, it was Stephenie Meyer impersonating the Bella I had created--bummer. However, Three Weeks With My Brother didn't ruin my image. It just gave a little background info, like "huh, that's where he got that idea".
Anywho, I give it my stamp of approval and would definitely recommend it if you are in need of a book to read poolside!