The only thing better than getting kids to read is getting them to read (and enjoy reading) profitable nonfiction. The Magic Tree House series isn't nonfiction per se, but it is educational without sacrificing that exalted element of children's fiction, Entertainment Value. The series recounts the adventures of siblings Jack and Annie as their magic tree house takes them (magically) to important events and people of history, as well as to witness important scientific research and discoveries.
Suitable for reading in any order, there are 28 titles in the original series covering everything from the American Revolution and dolphins to the Titanic and knights in shining armor. Each one is about 70 pages long and illustrated in black and white. The prose is fast-paced and engaging for young readers, and the stories feature fun plots usually involving the book's educational topic. Jack and Annie are realistic, if somewhat overly skilled children, and their adventures are similar to those most kids imagine themselves having in different times and places.
Following the initial volumes is the Magic Tree House Merlin Mission series (books 29-47, though the series is still in progress), slightly longer books featuring the same artwork and main characters. The ideas was to continue the series for slightly older readers so they could keep up with Jack and Annie as their reading skills improved.
A distinctive feature of the first 28 books is that important historical or scientific information is offset from the main text in bold type; the Merlin Mission books abandon this element, directly integrating the information in the story itself. It also emphasizes magic more strongly than the original series, though it's of the lighthearted goofy variety in all the books. The Merlin Mission books also tend to focus on people rather than events, and some of them are just stories.
For the Magic Tree House Research Guides, author Mary Pope Osborne enlisted the help of her sister and husband to compose companion books to the main series that delve further into the pure history and science of the topics. Illustrated with black and white drawings and photographs, these throw out any pretense of fiction and simply present nonfiction narrative and information in a fascinating way for kids. They can also be used as jumping off places for reports, or as prime book review material.
If you're looking for great literature this isn't the right place. If, however, you simply want books that are educational and will hold the attention of your K-4th grade kids, these are a pretty safe bet. Some parents may not appreciate the magic element, but there's nothing offensive here, no crudities, not really any discernible politically correct bent or blatant humanism, mostly just good clean fun. Good for fun time reading or as a supplement, the Magic Tree House Books are top picks of many kids, parents and teachers.