Help me! Harrow the Ninth [discussion]

Hi! I see lots of people talking about how confusing the 2nd book is. I’ve just read the first and am so excited to get into the second but am someone who can get quite confused ! So, without spoiling me do you think someone could tell me important stuff to keep in mind while reading to make sense of it? Like I think I saw someone say Harrow has schizophrenia and that influences the writing style??