"Angel of Darkness" by Dennis McDougal, about Randy Kraft and the other serial killers in the 1970s and very early 1980s in Southern California. Link: https://www.amazon.com/Angel-Darkness-Story-Heinous-Murder-ebook/dp/B002PXFY42
"Freed to kill", by Gera-Lind Kolarik (Author), Wayne Klatt (Author). A book about Midwestern serial killer Larry Eyler. https://www.amazon.com/Freed-Kill-Story-Serial-Murderer-ebook/dp/B00USC6V8K/ref=sr_1_1?s=digital-text&ie=UTF8&qid=1536896023&sr=1-1&keywords=freed+to+kill
"Bluebeard" by Valerie Odgen, a book about Gilles De Rais. https://www.amazon.com/Bluebeard-Valerie-Ogden-ebook/dp/B07H9KKXSY/ref=sr_1_4?s=digital-text&ie=UTF8&qid=1536896221&sr=1-4&keywords=Bluebeard
The Killer of Little Shepherds: A True Crime Story and the Birth of Forensic Science by Douglas Starr. Link: https://www.amazon.com/Killer-Little-Shepherds-Forensic-Science-ebook/dp/B003F3PMK2/ref=sr_1_1?s=digital-text&ie=UTF8&qid=1536895941&sr=1-1&keywords=killer+of+little+shepherds
The man with the candy, by Jack Olsen. https://www.amazon.com/Man-Candy-Jack-Olsen/dp/0743212835
"Deranged" by Harold Schechter, about Albert Fish. https://www.amazon.com/Deranged-Shocking-Americas-Fiendish-Killer/dp/0671025457/ref=pd_lpo_sbs_14_t_1?_encoding=UTF8&psc=1&refRID=JHBKDXB0BVQEGP8KN1A2
"Killer Clown: the John Wayne Gacy murders" by Terry Sullivan. https://www.amazon.com/Killer-Clown-John-Wayne-Murders-ebook/dp/B00BPVV2T6/ref=sr_1_1?s=digital-text&ie=UTF8&qid=1536896171&sr=1-1&keywords=killer+clown+Gacy
"The Want-Ad killer" by Ann Rule. https://www.amazon.com/Want-Ad-Killer-True-Crime/dp/0451166884/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1536896281&sr=1-1-catcorr&keywords=want+ad+killer
"Lust Killer" by Ann Rule about Jerry Brudos. https://www.amazon.com/Lust-Killer-Updated-Ann-Rule/dp/0451166876/ref=sr_1_2?s=books&ie=UTF8&qid=1536896309&sr=1-2&keywords=lust+killer+Ann+Rule
"Monsters of Weimar: The Stories of Fritz Haarmann and Peter Kurten" by Theodor Lessing / Karl Berg / George God. Link: https://www.amazon.com/Monsters-Weimar-Stories-Haarmann-Kurten/dp/1897743106/ref=sr_1_1?s=books&ie=UTF8&qid=1536896338&sr=1-1&keywords=monsters+of+weimar
"Strangers On The Street - Serial homicide in South Africa" by Micki Pistorius.
"Gruesome: The crimes and criminals that shook South Africa" by De Wet Potgieter. Link: https://www.amazon.com/Gruesome-crimes-criminals-shook-Africa-ebook/dp/B015JFIQH4/ref=sr_1_8?s=books&ie=UTF8&qid=1536896451&sr=1-8&keywords=south+Africa+crime+ebook
"Profiling Serial Killers: And other crimes in South Africa" by Micki Pistouris. https://www.amazon.com/Profiling-Serial-Killers-crimes-Africa-ebook/dp/B06XDCNQGR/ref=sr_1_6?s=books&ie=UTF8&qid=1536896451&sr=1-6&keywords=south+Africa+crime+ebook
"Murder in Tamden: when two people kill." by Paul Wilson. Link: https://www.amazon.com/Murder-Tandem-Paul-Wilson/dp/0732267730
"Australia's serial killers: Never to be released." by Paul B. Kidd. Link: https://www.amazon.com/Australias-Serial-Killers-Never-Released/dp/1743532253/ref=sr_1_13?s=books&ie=UTF8&qid=1536896675&sr=1-13