As soon as I got done reading this to the kids, my 15yo pointed out exactly what had been bothering me: it's not magical. The book starts with the children eating some strange berries (PSA: don't do this) and gaining the ability to understand their dog, Tee-Bo. They immediately accept this as their new life, and also conceal it from their parents and don't think to offer them the berries. Why? Because the story wouldn't work otherwise.
After that it's a straightforward burgler-type mystery, with the kids and their dog uncovering a ring of criminals. Think "That Darn Cat!" Which is fun, and fine, but really odd when you compare it to the second book, TEE-BO THE TALKING DOG LEADS THE WAY IN THE GREAT HORT HUNT, which is full of talking animals, magical creatures, mysterious amulets, and hidden worlds. I read the second one many times as a child, my older sister had bought it from a grocery story when she was wee, and it was a family favorite. A couple of months ago she gave it to me to read to my kids, and we loved it, and also noticed that there is a big #2 on the spine. My sister found a copy of this one online and ordered it immediately. So it's fun to have both books (there appears to be no book 3), but I must admit I prefer the second.
Sidenote about our personal copy: This book smells. The seller clearly tried to clean it up (maybe it smelled like smoke?) by wiping the book down with something that smells strongly of chlorine. With just a hint of potting soil. My kids and I can't stop sniffing it and discussing. I have never encountered such a thing. What did they use? and why?
I remember the first time I saw this book was on Christmas morning! I loved it so much I had finished it by the time I went to bed that night. An absolute charming tale that I read over and over until years later, the book fell apart.
Another book I added because of Melissa Harris Perry's wonderful suggestion to revisit books you loved as kid. I read this until it fell apart, and then I taped it together and read it over and over, until I started losing pages. Can't wait to revisit it!