According to Dean:

“This was one of four completed works sold with the assistance of a friend and editor to a West Coast erotica publisher that was launching a new imprint that was supposed to be legitimate and mainstream. The four books were all sufficiently mainstream (not at all erotica) to have been submitted to New York publishers, and two of them came close to selling. Without my knowledge, these four books were completely re-written.”
Source: Letter to the author

“In 1969, Dean agreed to have a small publisher publish two of his non-fiction works (one entitled THE SICK SOCIETY and the other entitled GOING UNDERGROUND) and two of his fiction works (one entitled HUNG and the other entitled TIGER 650). All four books were presented to the publisher as finished manuscripts and Dean fully expected for them to be published in the form submitted to the publisher. Unfortunately, all four books were put into production before Dean learned that the publisher had arranged, without Dean’s knowledge or consent, for them to be so completely rewritten that none of them, as published, bore much resemblance to the original manuscripts as submitted by Dean. Although he wasn’t able to stop publication, he did get the publisher to contractually agree to publish all four books under a pseudonym. The publisher further agreed to indemnify Dean against claims arising from the material added by the publisher: “Author and Publisher acknowledge that…the Work will be published with material changes from the original manuscripts of same, that the Publisher assumes all liability for the content of those new chapters and passages.” However, only one of the four books was published under a pen name- HUNG was published under the pen name Leonard Chris. THE SICK SOCIETY manuscript was published under the title PIG SOCIETY, the GOING UNDERGROUND manuscript was published under the title THE UNDERGROUND LIFESTYLES HANDBOOK, and the TIGER 650 manuscript was published under the title BOUNCE GIRL- all with Dean and Gerda Koontz as the credited authors, and therefore in breach of Dean’s contract with the publisher. Copyright Office files on all four of these books now reflects affidavits from Gerda and Dean stating that (1) Gerda did not participate in writing any portion of these books and (2) Dean disavows any claim of authorship or responsibility for the content of these four books due to the substantial nature of the unauthorized changes to his original manuscripts.”
Source: DeanKoontz.com