Mary Pope Osborne's 39th addition to her 'Magic Tree House' series, DARK DAY IN THE DEEP SEA tells of Jack and Annie, who have to find one of the four secrets of happiness to help save Merlin the magician. But when they find themselves on a misty island, they wonder how they can find anything - and when a pirate ship turns out to be the world's first floating science lab, an even more exciting expedition results.

We have the complete series of MTH books, both the simpler paperback ones and the Merlin Series hardcovers. Currently my (almost) 8 year old son is ensconced in the books, but my 11 year old read this book as well just because she wanted to say she's read them all (granted, it took her less than an hour to finish the whole thing, but she is reading at the 7th grade level so no surprise). Both really enjoyed the story, said it is one of the better story lines in the Merlin Series, interesting, creative, etc. Highly recommend.

OK, I'm not reviewing this for myself, although I do enjoy the concept and the stories, but for my (nearly) six year old grandson. He simply adores this series by Mary Pope Osborne...except...at the start of each adventure, when the tree house moves and then stops...when it says..."then everything was still...absolutely still"...anyone remember Abbott and Costello's "slowly I turn, step by step..."?
He just plain squeals when anyone either reads him that part or just starts the quotation (he loves it, though!)
The series shows great imagination (if you can "get over" the part where "magic" is involved. Sometimes I think we lose sight of the fact that magic is simply a storyteller's device to see a different angle of the story or to introduce elements that are more imaginary. If you believe it exists, it does...if you don't, it doesn't) and helps kids to come to grips with cooperation and a bit of self sacrifice, as well as helpfulness. (I don't know about you, but I struggle with that myself, and for our current generation of kids, they need all the help they can get!)
And, quite frankly, I bought it for the grandson because of the Octopus on the cover. He is enamored of this particular sea creature, and the story did not disappoint. (although we have read over 20 of the rest of the series as well, and he only found fault with one that I can remember, and I can't recall which title that was...)
As soon as his mom had read him this one (it was a birthday present), he wanted it read to him again, and that to me says that it hit the right note with him.
The "Magic Tree House" series is a grand adventure for all concerned. It enthralls the younger readers (or being read to), and is a joy for the parents to read to their children or grandchildren. Covering all sorts of adventure and relationship topics, as well as great brother-sister dialogue, it's just plain fun!

the lesson in this book is about compassion for creatures we may not know much about; which takes place in the 1800's and scientists on the HMS Challenger, which really existed, as did the scientist Moseley. This was a time of exploration for scientist and a field that opened up called oceanography. My four year old enjoys these books immensely. This was not one of his favorites, but he still rates it as a "love it."