There are several other reviews that cover the good and bad. So I'm just going to give my immediate thoughts:
I read After Ben not more than a week ago and I was so confused with who was who in Saving Sean. And who I thought someone was didn't match their personality in this book. Except for Marco, Italian or not, nice or not, someone (Theo)should tell him he's an adult and its unacceptable to crawl into other peoples beds, unless invited.
Maggie was a great friend in After Ben however she was a horrible sister in Saving Sean. The two don't match up at all. And personally I would have told her to shove it, life is hard and you shouldn't rely on anyone/anything else for financial assistance.
Peter wasn't a blurter in After Ben.
The whole tree thing/land thing/hoarding thing was confusing and repetitive and boring.
Peter and Sean, no clue where that romance/love came from or was going too except to bed. Couldn't figure out why they even liked one another.
And Sean's constant running when he can't handle something? Yeah that was silly.
I loved loved loved After Ben. It wasn't perfect and no book really is but it had characters with stories and hearts. This book had stories but no real heart.