Adult Thriller/ Suspense, Epistolary. Stalker/ serial killer becoming increasingly obsessed with woman, told in memos and answering machine messages, black book with red writing in typewriter font. Read sometime in the 1990s. > Likes and Comments

Typical storyline of stalker becoming more and more obsessed with his victim/love interest, but told through memos, answering machine messages, notes, etc. Read in mass-market paperback, had black cover, lowercase typewriter font in red for title and author. Read in the 1990s, probably mid-90s.

Fan Mail?

Maggie is still looking for this book:

"Adult Thriller. Epistolary, read in the late 1990s. Murderer/ serial killer.

I don’t remember names of characters; fairly standard thriller plot of trying to stop a serial killer before they kill again. What was unique to me was it was told in scraps of emails and faxes (as well as memos and notes) when that was still fairly new to the general public. I remember it as a mass market paperback with a black and red cover but that may be wrong."

Google Books has a limited preview of Fan Mail by Ronald Munson - arratavy's suggestion. You might get lucky searching for keywords:

https://www.google.com/books/edition/...

Publisher: "In a thriller narrated entirely through e-mails, letters, faxes, messages, memos, and transcripts, beautiful newscaster Joan Carpenter is stalked by a crazed fan"

There are different cover images.

If it weren't for the then-contemporary elements, you could be describing Bram Stoker's Dracula. :D