The "book" is accompanying studying material for the course Probabilistic AI at ETH Zurich. Essentially each chapter is the material covered in one lecture (3hrs).
There is no independent scalar floating point unit for most modern CPUs. When scalar floating point arithmetic is needed, it is send to the SIMD unit. This pretty means that scalar and vectorised floating point operations usually have the same latency. If you do any scalar floating point operations, the CPU is just doing vectorised operations except with only 1 useful value.
If every other exchange is selling $AAPL at $100 and suddenly the top level of one exchange drops to $99, then if you just take out that order you basically gain a free dollar. Do this very fast and have pricing the product accurately and you will print tons of money.