(Book spoilers ahead!)
I think we can all agree that the majority of the parents from the TV show are shit - The Montgomeries are totally useless and let their daughter date her high school teacher, The Hastingses and DiLaurentises are... I cannot even describe it. The Fieldses, while probably the best, still have the mishap with Emily's coming out on their record, and Ashley, while incredibly supportive and loving to Hanna, was truly reckless at times.
However, their book counterparts are truly something else. I read all 16 books 3 years ago and only re-read the first few since then, but from what I remember... they were just simply evil.
After A revealed to Ella that Byron had an affair with Meredith, and that Aria knew all along, she kicked Aria out of their house alongside their father, and Aria was forced to live with her father and his mistress. Ella also completely ghosted Aria for weeks and didn't call her, nor did she pick up when Aria called. She also dated a guy named Xavier, who was EXTREMELY creepy and predatory towards Aria; I don't really remember how that situation was ultimately resolved, but Aria moved out once again from Ella's house and back to Byron's because she was so creeped out by Xavier.
After A outed Emily to the whole school (and additonally, her family), her parents first sent her to some sort of conversion camp, while also totally ignoring her and treating her like a ghost. Then, when that didn't work out and they caught her kissing Maya at some random party, they SHIPPED EMILY OFF to live with her Puritan uncle and aunt. They only accepted Emily once she ran away from her Puritan family's house and went off the grid for a while. Still, I remember that in one of the later books, after Emily is presumed dead, Pam doesn't want to let Spencer, Aria and Hanna attend Emily's funeral, calling them "bad influences" and kind of blaming her for Emily's death.
The book version of Ashley, while not really a malicious monster like the rest of the parents in the book, just simply doesn't really care about Hanna. She's incredibly involved in her business and just doesn't really spend time with Hanna. In one of the books (I think the fourth or fifth one?), she straight up leaves for Singapore for a whole year, leaving Hanna in their house, while Tom and his new family moved in. Tom is pretty similar to his TV counterpart; he leaves Ashley and Hanna when she's in middle school, doesn't talk to her ONCE for THREE YEARS (!!!), and highly favors Kate over Hanna.
And the Hastingses... oh my god. Truly, TRULY despicible people. They do not care about either Melissa or Spencer in the slightest, except for when it's convenient to them (so for example, when their daughters exceed academically or socially). When Spencer stole one of Melissa's old economy essays, she was nominated for a Golden Orchid award, which is like, the biggest academic achievement you could get as a teenager. Well, her parents found out that the essay was in fact Melissa's, and while dissapointed, they forced Spencer to stick to the lie and shut up about it. Well, a little later, Ian is arrested for Alison's murder; Melissa finally comes clean to the police about how the two really spent the night, and Spencer, inspired by her sister's honesty, comes clean to the people that assign the Golden Orchids just as it is revealed she had won. The whole thing blows up - EVERYBODY finds out about the scham, and it's a total humiliation for the family. Peter and Veronica fully ice out Spencer, not talking to her, ignoring her, or just being flat out mean and evil to her face. This pushes Spencer so far as to begin suspecting she is adopted (hence why her parents favored Mellisa), after her grandma excludes her from her will; with Andrew Campbell's help she finds her biological mother, who turned out to actually be a surrogate, only to be once again screwed over by a parental figure; her surrogate mother, Olivia, extorts money from Spencer and disappears. Peter was also involved in a years long affair with Jessica DiLaurentis, which resulted in the birth of Alison and Courtney. I'm pretty sure there was way, way more, but I've only re-read as far as the sixth book so far.
The DiLaurentises are also despicible people. They hid Courtney's existence from the world after admitting her to a mental hospital, and highly suspected (and perhaps even knew) that Alison was the one that killed Courtney, even though (I think?) Jessica tried to frame Spencer for the murder in the books. After Alison (the ACTUAL Ali) is on the run for attempting to kill the girls multiple times, it turned out that Jessica was the one hiding her.
