A blast from beginning to end, "「ミステリーの館」へ、ようこそ" is a book for children that everyone can enjoy. Kaoru Hayamine writes easy to read, fast-paced, with lots of humor stories, and this one is not an exception.
The story is simple as they come. Reiichi wants to go on a date with Ai, but her two sisters, and Great Detective Yumemizu, and even Itou-san end up joining them, all of them going to a theme park together. There they get a puzzle that, after Yumemizu solves it, gives them a phone number. After they call to the number, they discover that they have been invited to a new challenge. A real mystery awaits them.
From page one, the story is full of twists, funny moments, great characters and a playful and joyful style that is easy to enjoy. The mystery is not particularly complicated, but it has a couple of nice twists, and it is always enjoyable, keeping the reader's interest. The pace never slows down, and Kaoru knows very well how to develop a story. Many books don't have a plot so well thought and developed as this one.
This is a clear example that a book for 'children' can be enjoyed by everyone.
The mystery is slightly more interesting in this volume than in the first volume. I still love the characters, but Hayamine Kaoru adds an annoying bit to Yumemizu's character. (I can't remember if he already did this earlier in the series, but at least it wasn't there in the first volume.)
I think Yumemizu's character, as he was presented in the first volume and continues to be in the series for the most part, is perfect. Yumemizu is a genius who doesn't conform to societal standards. He doesn't hold a proper job. He probably owns one set of suits--the same one he always wears. The only pieces of furniture in his Western-style home are bookshelves and a sofa. But he's kind and virtuous; as a definite mark of his virtuosity, his friendship with the triplets was firmly established at the beginning of Volume 1 and has never wavered. Like many detectives of detective fiction, this is not a character that needs to grow or change; his flatness is not a problem in this genre.
However, at the end of the book, during his private conversation with the (real) culprit, Yumemizu says he longs for a different world--a longing that his culprit seemingly understands and commonly refers to as their "red dream." I didn't like this when I was a kid, and reading this now as an adult, I think it feels tacked on and dissonant with other facets of his character. It would be more in line with Yumemizu's character to point out the foolishness of wishing for a world that doesn't exist; in the book, a third character gets to wise up and point out he's a fool. This vain effort on the author's part to add complexity and dimension to Yumemizu leaves a bad taste in my mouth because it implies that Yumemizu doesn't care about his friendship with the triplets and is ready to leave them behind despite all the evidence to the contrary.