I ordered a few books of this series for my six-year-old son. I won't be ordering any more. I'm placing my review on this book, because this one was the worst of the three we bought.
There is potential in the concept of two children returning to various bygone eras, and experiencing them first hand. The character of Jack, if further developed, could be a good role model for kids interested in science, history, and research. But the character of Annie doesn't work at all. I think she is intended to be a foil for Jack's more serious, contemplative personality, but if she had been portrayed as smarter this would have worked better.
The plots in this series are surprisingly dull. My son halfheartedly suffered through the first read-through of each of the books we bought, but he doesn't want to read them again. We then checked out "Dinosaur Habitat" by Helen V. Griffith from the library, and he asked to read that book at least fifty times.
Osborne underestimates the intelligence of her audience. On occasion, the stories seem to telescope into Annie's eye view, and a lot of ink that could have been devoted to the various interesting aspects of dinosaurs was instead devoted to their relative "niceness".
My most serious objection, however, is the bad grammar. Do not believe the notion that your kids need their sentences cut into pieces in order to read them! Beginning readers pay a lot of attention to structure. A well written, grammatically correct sentence is filled with structural cues which help new readers decipher unfamiliar words. "Dinosaurs Before Dark" contains so many errors, I consider it worse than useless as a teaching aid.
I don't enjoy writing negative reviews, but I want to warn other parents who might be attracted to this series as I was.
* We did enjoy the illustrations by Sal Murdocca, and only wish they had been in color.