I don't know why, but I've had a hankering for 1970s DC these days. I recently bought 2 other Showcase Presents, Batman volume 5 and Ghosts. I didn't experience these comics when they came out, so I've always been a little fascinated with them, mainly because they always had such cool covers.
Secrets of Sinister House was originally called The Sinister House of Secret Love for its first 4 issues. Issues 1-4 were also double-sized comic books with one main story, and one brief back up comic, making them essentially graphic novels. These early issues had a definite horror/romance slant to them, usually involving a woman marrying an enigmatic or super attractive dude only to find out he was cursed or was in league with the devil. It was all in good fun.
From issue #5 to the end of its run at #18, the title of the book changed to Secrets of Sinister House. #5 was the last issue in the romantic horror graphic novel style, with #6 introducing its new format of 4-5 shorter tales in a normal length comic book. Eve, the mom of DC horror commentators Cain and Abel, also showed up to introduce each story Cryptkeeper-style, sometimes even becoming a character in the action. After issue #5, the stories shifted away from romance to standard scary stories involving werewolves, ghosts, and monsters. But here and there, some pretty good yarns unwind themselves that rely more on suspense, mystery, and clever endings.
Funnily enough, I actually liked the initial horror romance format of this book better. It just seemed like the writers could develop the stories better and and the climaxes had more power because of it. With #6 on, the stories became so short that the plots became ridiculous. It would go something like this. Guy is in woods, gets bit by werewolf, becomes werewolf, gets shot, the end. It's almost like watching teaser trailers of a full-length horror movie. Or they seem like story ideas, not stories themselves. It's a real shame because a lot of those issues contain some gorgeous art from some I have heard of like Don Heck, Larry Hama, Alfredo Alcala, Howard Chaykin, and Gil Kane, and some I haven't heard of like Rubeny, Alex Nino, and Jess Jodloman.
Definitely worth a read even though you will probably be disappointed with the writing of the greater half of the book. Appreciate it more for the art and the unintentional rushed humor.