The first volume, Life and Death By the Numbers, contains 45 life-and-death problems. In each problem, the black stones are shaped like a number between 1 and 40.

It's more or less what you'd expect from that description. Yilun Yang is good at designing go problems; so these are solidly-constructed go problems. They'll test your skills, and you can learn something from them.

But the down side is that the shapes involved are fairly artificial. Sometimes, the shapes almost seemed like they might show up in real games; much more often, however, the shapes didn't seem realistic. For example, in the two-digit problems, there are two separate but sizeable groups of stones, with some sort of more-or-less solid connection between them; I don't see two adjacent groups of stones like that in my games very often. Similarly, a digit like '6' might be broken up into 5 groups of stones with diagonal connections between them, with some of the key points occupied by white stones and some of them not connected; while a single diagonal connection is the most natural thing in the world, having 5 groups in close proximity thaht are all related to each other by diagonal connections seems a little weird to me.

The problems are in numerical order (covering each number from 1 to 40, some of them getting more than one problem); unfortunately, this isn't the same order as their order of difficulty. They range in difficulty from 10 kyu to 5 dan, but they jump around in strength. (Admittedly, it's not as bad as it seems, since most of them have their difficulties right around the kyu/dan split; outliers like 10 kyu or 5 dan are rare.) Also, for what it's worth, I thought the problems were a little harder than indicated; this probably has something to with my feeling that the problems were artificial.

So if you're looking for a well-done novelty book, this is for you. But if you're looking for a book to use to study life and death, I would look somewhere else.

It's a small book, and fits in the pocket of my jeans.