I am going to review all three of these ("Peter and the Starcatchers" "Peter and the Shadow Theives" and "Peter and the Secret of Rundoon" in one review.
I loved all three of these books. They make wonderful prequels to the original "Peter Pan" story and set up how Peter became, well, Peter! There are little hints that refer to things to come which are enjoyable (oh that's how Neverland became magical, that's how Captain Hook came to be and hates Peter, etc) So as a fan of "Peter Pan" these three books were lots of fun, and have a nice story in of themselves to tell.
I will add - DO NOT read any of the books past the 3rd ("Secrets of Rundoon") because the 3rd book wraps up everything nicely and leads into the original "Peter Pan" just so. The fourth book breaks all of that and messes up all the canon and timelines and is simply not a good book! I was disgusted with it that I haven't ventured past book 4 to see how the other in the series go. So - do read this if you like Peter and Neverland, but STOP at book 3!