If you want to see what he is talking about in terms of how delta and gamma are affected by time to expiration ("spikey"), you can take a look at the apps here: https://www.5minutefinance.org/concepts/the-greeks
Option Volatility and Pricing by Natenberg is extremely complete while managing to avoid drowning in maths, it is widely recommended and considered a classic. There are more informal books around that focus a little too much on trading/application rather than mechanics, and an endless supply of textbooks that'll either bore you to death, drown you in maths or both.