These small format 32 page glossy booklets pack a lot of information into each volume. They are tagged as being suitable for grades 4-6 and for readers of lexile 630 to 740. I don't know anything about lexiles, but these books strike me as being more suitable for grades 3-5. I would hope 6th graders would be nearly ready for something a bit more advanced than these simple books. They are full color with lots of interesting graphics -- photographs, maps, letters, diagrams. They don't talk down to the readers, although two of the books use more exclamation points than you normally find in history or text books. There is a glossary in each volume and suggestions for individual and group activities based on the content. As for the historical content, it's accurate if a bit simplified -- the account of the Donner Party doesn't gloss over the possibility of cannibalism. but it doesn't dwell on it, either. I suppose it's inevitable that the Junipero Serra volume would receive the most criticism and here's mine -- the author is decidedly pro-Serra while briefly acknowledging why Serra is "controversial." It would be nice if sources were cited and further reading was suggested, but these are grade school resources after all, and presumably the teacher or home schooler will be able to point students in the direction of the library for more information.