Do I have to change names / disguise identities in an autobiography to avoid legal actions based on slander, liable or defamation of character? Are those the only basis? Can someone get an injuction against the book?
What if it's true (according to my memory)? Some of the people or their estates are powerful people - one is super famous and powerful and still alive. I could also see some ex-girlfriends & friends possibly objecting to the book. Can I write anything I want about anyone? How do I protect myself and the book? Thanks.
Truth is not necessarily a defense, especially if the other person has a different memory/experience. For example, "I once loved Suzy Smith, but she left me for a nerd."
Maybe that is the way you remember it. Suzy on the other hand, might remember "I left him because he was an abusive jerk." The dead cannot claim defamation rights. Their family might if they are mentioned and are still alive. Sometimes a work of fiction is so thinly disguised that the target can go to court and say "This 'Suzy Smith' is really me Mary Jones, and I resent being portrayed as a cold, heartless woman."
There is always a risk in all autobiography. The best way to go is to to have a lawyer review the work prior to publication.
The questioner might find some of my legal guides helpful:
From my legal guides on law in general and about attorneys
Is it Legal? Is it Illegal?
Selecting and Hiring a Lawyer
Understanding the Different Court Systems
An Introduction to Legal Terms used in Litigation
Mr. Sarno is licensed to practice law in NJ and NY. His response here is not legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter in question. Many times the questioner may leave out details which would make the reply unsuitable. Mr. Sarno strongly advises the questioner to confer with an attorney in their own state to acquire more information about this issue.
There are lots of potential consequences, and at elast 3 potential claims, especially if you plan to dish some dirt. The safest course of action is to secure "life rights" agreements with everyone mentioned, but I imagine that that's impossible or impractical.
Since no one owns history, you're theoretically free to recount actual events, but the problem is always going to be that memories are flawed and indisputably selective things, so no 2 people are likely to remember the same event the same way. If you wrote anything that's unflattering about anyone, whether you think it's a TRUE FACT or not, if you can't show hard proof of it, or it's not unquestionably your OPINION rather than FACT, you could get sued for defamation.
While truth is supposed to be an absolute defense to defamation, even the truth can violate someone's privacy rights by disclosure of embarassing facts.
And if you use any of these famous people's names or images to market the book, there are also publicity rights to be concerned about, since you can't use anyone else's persona for commercial exploitation.
In short, you should have your book "vetted" by an entertainment lawyer, and/or by your publisher's editor, who will no doubt insist that you agree to indemnify them for any violation of these rights. A lawyer can help you protect yourself against a successful lawsuit, although no one can stop anyone from suing you to try to bully you into not writing this book.
Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.