The plot moves along well, and the characters are likeable. It took me 2 chapters to remember all that had happened before in book 5, so I suggest a quick review of that book before reading this one.
Will and Horace do quite a bit of needling each other and they have brief arguments, very indicative of a long-term best-friendship, especially one under pressure. I enjoyed Will and Alyss as they were apart the entire book, but their relationship still moved forward. This book is on a grades 4-8 level, and the book is not "mushy-mushy" at all. It does deal with saying "I love you"--and how that might complicate things between friends (especially Will/Horace/Evanlyn). The book has a great resolution, and does not set-up events in Book 7. Book 7, Erak's Ransom, is going to take place in the years before books 5 & 6.
Ranger's Apprentice has already been released in Australia, and books 7-10 will come out in the United States within the next year. They are being released at a pace of about 4 months apart. They are in hardback in the US, where in Australia, their original print was in paperback. Happy reading!