The Map of Stars (York #3), by Laura Ruby, for Timeslip Tuesday

If you are new to Laura Ruby's York series, it's a bit of a spoiler to see this third volume labeled a time travel book. If, however, you've reached the end of the second, you'll recall that in the course of following the mysterious clues of the Morningstar Cipher, that has sent them diving into New York's past, and into danger, twins Tess and Theo found a picture of their older selves from the 19th century....and have no clue how that happened.

This is where The Map of Stars begins (Walden Pond Press, May 2020). Tess, Theo, and their good friend Jaime have made considerable progress unravelling the cipher, and have "borrowed" the many tangible bits and pieces of strange and interesting stuff they've found along the way. The path ends with a set of plans, and all the things they need to build it...All along the way, greedy and powerful men and women have been working against them, and strange and unexpected allies, both living and dead, human and not, have come to their aid.

This third book has just as much tension as the first two, but ratcheted up a notch. As well as the physical dangers of their antagonists, there are glimpses into another timeline, in which the twins, now older, live in our own world a few years in the future, and is a sad and scary place....So yes, there is time travel, in this case as a fixing mechanism that creates a new timeline. I was able to make sense of it all, once I figured out what was happening. It's more time travel in the function of plot than time travel that shows the past, or shows the characters coping with it, but that's fine. The plot and the great characters and wonders of the alternate New York are plenty!

The books are long (this one is 514 pages), and very detailed, and having read them over the course of several years as they came out, I found my memory spotty, which was a nuisance, though Ruby does a solid job making sure the important events/clues/characters, etc. are reintroduced. Not all middle grade kids will have the reading stamina to make it to the end. But for strong readers (of all ages) who love books with smart kids and treasure hunts, this series is a treat! There's humor and lots of bright and sparkly stuff, entertaining interactions between characters, and strong messages of social justice that make the pages turn quickly.