I have recently developed an interest in demonology and I'm looking to study it from a Jewish perspective. Can anybody recommend books on the topic?
Belief in demons exists in Judaism but is very peripheral. Many leading Jewish thinkers thought they didn't exist while others felt they did exist but we should distance ourselves from the occult.
The only book on the topic I am aware of is Ascending Jacob's Ladder: Jewish Views of Angels, Demons, and Evil Spirits by Ronald Isaacs
For this subject, I'd most definitely recommend this book:
The "Minhat Yehuda" by Rabbi Yehuda Fetaya
Important: First and foremost, sorry for this long rant, but I really loved this book yet I hope it will answer your questions without petrifying you (like it kinda did to me on the first read). It's actually Rabbi Yehoshua Zitron (who gives amazing classes on Youtube) that suggested it to me.*
TL;DR: It's seriously a read that's not for the faintest of hearts, as it deals with what I'd call the precise laws & mechanics of the "metaphysical judiciary system" (i.e. what happens between a soul's passing to the other side, and its final destination in the Gan Eden and/or next Reincarnation), which, to bear in mind, is all set with the very best intention for one's soul. It all starts from people being possessed and Rabbi Fettaya healing those poor souls hiding in people's body, the evil spirits that pursue them, and some other interesting facts about the different realms / spiritual planes, and "Surgeon Angels".
It might sound corny, but if if you're not in a happy mood, alone at night, or particularly stressed and worried, just refrain from reading it for the time being, as it can be really overwhelming.
That said, keep in mind that nowadays we're living in an era that's waaay out of touch with what it really should be, and we're all judged according (and relatively) to the "spiritual level" of our generation, and this book was written in an era where people were way more "tsniut" (modest / humble) than in our generation, specially in the impudence, promiscuity & temptation departments. Compared to the late 18th century, we're reaching the "49th level of Tumah" (impurity): in other words, we're all influenced by an opaque veil of futilities in a way or another, but the good news is G.od and his "Celestial Court" are well aware of it, which somehow weighs in our favor.
If you're not very versed in the study of Torah, I'd strongly suggest to start the book with last few chapters (after having read the intro), which deals with 'Hidushim (novel Torah teachings on the Parashiot / Torah portions of the week), general Jewish Wisdom, and some other precious advices. Keep in mind that G.od is very patient and forgiving, and that Teshuvah / Repentance is at reach to anyone who's genuinely asking for it.
Hope this helps!
Go buy an artscroll edition of Tractate Pesachim of the Talmud, and go to page 109b from the words ולא יפחתו לו…artscroll has a great intro into the different beliefs about demons that basically takes up the whole page, and the Talmud itself spends numerous pages talking about demons and superstitions