米澤穂信 (YONEZAWA Honobu, born 1978) is probably best known outside Japan for a series of everyday life mysteries, starting with 氷菓 (hyouka, Ice cream, 2001), which were the basis for an anime series of the same name. I've only seen the anime series of this; but judging from that 春期限定いちごタルト事件 (shunkigentei ichigotarto jiken, The Spring Term Special Strawberry Tart Case, 2004) is very similar. This book is also a series of "puzzles of everyday life", solved by a boy and girl who have just started high school (which in Japan would make them probably fifteen years olds´): the teenage narrator, 小鳩 常悟朗 (KOBATO Jougorou) and his friend 小佐内 ゆき (OSANAI Yuki).
Kobato and Osanai were at middle school together, and various unfortunate experiences there have led them to adopt a life philosophy, which they describe to themselves as aiming to become a perfect 'petit bourgeois'. In practice this means keeping their heads down and not doing things that might attract attention. In particular, Kobato tries to avoid showing off his skill at deduction. Osanai behaves like a reserved and timid child, very dependent on Kobato and only showing enthusiasm for desserts. What part of her character she is suppressing only becomes evident in the course of the book.
The 'life philosophy' will probably make older readers roll their eyes a little; but you could say it is a realistic reflection of the things teenagers do. The stories are all mysteries, but they make a comedy of school life. Kobato comes across as a somewhat intellectual type, at any rate a student who reads a lot and pays attention in class. This occasionally makes the Japanese a little more difficult than you might expect for a reader who doesn't come equipped with this standard knowledge. There is a certain tendency to melancholy in the stories, a suggestion that the main characters are suppressing part of their own nature; but comedy is prevalent. Despite the reliance on certain "types" from popular literature, this is generally pretty successful.
Kobato of course does not manage to avoid getting involved in mysteries, and throughout the book he solves a series of mostly minor puzzles, often pulled into them by a busybody friend from his primary school days. Some involve a real (mostly very minor) crime but others are merely puzzles. Most notable is a chapter devoted to finding out how someone managed to make cocoa using only three mugs and one teaspoon (but no milk pan), which is played as a kind of 'impossible crime' type puzzle. As with many such short story collections in Japan, there are developments over the course of the book, a gradual revelation of Kobato and Osanai's characters and background, and an overarching mystery which comes to a high point in the final chapter.
The mystery aspect is generally good enough. Although nothing stands out as a classic puzzle, the surprise for the reader at seeing where the carefully laid preparation is leading is real. And the mix of school comedy and mystery allows for some pleasing humour about what constitutes a reasonable deduction.
The book is the first in a series of three (one for each term of the Japanese school year). I owe my awareness of it to Ho-Ling's blog. You can read his review there, as well as a review of the second book in the series (which I haven't yet read).