In short none;
In modern cryptography, we work in Kerckhoffs principles. In which, the adversary knows everything but not the key. You might be followed which book you've bought, someone's visited your house to see your bookshelf, etc. You should assume that the adversary also knows your randomness source, in your case, it is the book and key derivation method from the book. Therefore, your system is not secure.
An interesting example is Dual_EC_DRBG a pseudorandom number generator scheme. You think that it is a good pseudorandom number generator scheme but, not. It is backdoored by No Such Agency.
A good key generator scheme must resist against all above or even more. The common way is using a true random number generator to generate random numbers. A true random number generator is unpredictable even the adversary has the same system.
See also; Where do key generation algorithms take the randomness from?.