# What is the Spectral Form Factor?

In many papers in Random Matrix Theory [1-3] related to quantum chaos (and, in particular, to the SYK model) they analytically continuate the partition function of the system $$Z(\beta)$$ into $$Z(\beta + it)$$ and then define the Spectral Form Factor like

$$$$g(\beta,t)=\langle Z^*Z\rangle$$$$

They then claim that the specific shape of this function gives a lot of information about the level statistics of the system. Is there any paper or book where I can read a good introduction on these tools? Every paper I found doesn't explain anything in great detail and just shows graphs.