In this series, 8 year old Jack and his 7 year old sister Annie travel to a different time period in each installment. The series begins with Dinosaurs Before Dark in which Jack and Annie find a tree house that has mysteriously appeared near their home in Frog Creek, Pennsylvania. In the tree are lots of books. In one particular book, Jack and Annie see scenes of various places and time periods. At the page of the dinosaurs, they say they wish they could go there. Then, presto-magic, the tree house plops down in the middle of dinosaur time. They explore the dangerous land are helped to return to the tree house by a friendly pterodactyl. The whole experience is completely mysterious to them (how did we get there, who owns the tree house), but they have one clue: a medallion with an "M" on it that they find on the grass.

In subsequent installments they find out that the tree house is owned by Morgan LeFay of King Arthur lore. She is a librarian for Camelot and travels about collecting books. Each time the children enter the tree house they take off on another adventure. Every four books in the series deals with a theme or problem that the children have to solve.

• Books 1-4: meeting Morgan and finding out what she is all about.
• Books 5-8: finding clues and artifacts that will release Morgan from a spell cast by Merlin that turned her into a mouse.
• Books 9-12: solving riddles to pass the test to become Master Librarians.
• Books 13-16: saving books from four ancient time periods that would otherwise be lost forever.
• Books 17-20: rescuing a mysterious dog that is under a magic spell.
• Books 21-24: finding 4 special kinds of writing for Morgan's library in order to save Camelot (something to follow, something to send, something to learn, something to lend).

Jack and Annie are good foils for each other in the stories. Jack is cautious and reflective, always taking notes about the things he sees, or reading about them. Annie is more adventurous, jumping right into the action of the time period. For a few of the books, Mrs. Pope's husband collaborated with her to write non-fiction companions. The books are short enough to not be intimidating for new readers and interesting enough to keep them wanting to read more. My boys love them and read the new titles that come out even though they are much below their reading level now. They are intrigued by figuring out the kid-sized mysteries.

Some Christian groups have banned these books because they deal with magic. I did not find the use of magic offensive. There is no spell cast in the stories; we just hear that Merlin cast a spell. In fact, I thought it was kind of quaint and cute that Morgan LeFay is cast as a librarian.

In some of the stories, Jack and Annie have to learn about the religious or spiritual aspects of the time they have landed in. So, in Night of the Ninjas, they have to act out the Ninja way in order to make it through the forest without being caught by the bad guys (use nature, be nature, follow nature). In Buffalo Before Breakfast they have to imitate the ways of the Indian. This may cause some people some concern, but my children thought of it as merely historically interesting. The stories incorporate some vital historical information about the time period in which they travel, which Jack is always stopping to write down. This includes the religious beliefs of the people. When they travel to Pompeii to rescue a book, Jack reads from a research book about Ancient Roman times, including gladiators, the forum, public bathes, and myths of the gods and goddesses.

One thing I was concerned about was that occasionally in the stories Jack says about Annie's lack of caution, "I'm going to kill her." I was hoping my children wouldn't start saying that! And they haven't. One thing I wish they would imitate, though, is Jack taking notes or looking things up all the time.

These books are a good 2nd grade level reading bridge between just learning to read and harder books that can be tackled in 3rd grade. They are purely for pleasure reading!