To me its senseless to buy books on Chinese air power as things are moving so fast in China that by the time the book hits the shelfs the information in it is already outdated.
The best place to keep track of Chinese military development is on internet forums like SDF.
Most people are not dedicated to search through forum posts and piece things together to stay up to date on info and number anyway. I think you'll find that people like us who frequent sinodefence as members are quite a small minority in the population. Even if someone had known about this place to look for info it takes what, maybe a couple of months of absence to lose track of where things are? So they would want a book for easy consumption. And if info goes out dated then economics would suggest some sequels and further editions .
I wonder, is there some sort of scheme where people can buy an online book regarding certain time changing topic, then have a sort of arrangement where they pay small amounts to received updated downloads every now and then.
Deino's Chinese air power monthly subscription perhaps?