I'm a tough critic when it comes to books. I have no problem posting a less than glowing review for a best-selling author. They usually have so many great reviews and such a huge following that my piddly opinion won't affect their career too much and it's also likely that they've developed a tough enough skin to withstand whatever problems I had with their stories.
However, when it comes to authors who haven't reached that level of success yet, I hesitate because I know how much reviews can affect sales. I just read a paranormal, erotic romance that was pretty disappointing. I read half of it before giving up. Because I feel this inexplicable need to express what I didn't like about it, I'm going to do it here without naming the book.
It started out strong. I liked the hero--he was sexy, smart, focused on his goal, mysterious. The heroine had pluck, she was strong-willed, talented. But somewhere along the way I became annoyed with the lack of info about the paranormal aspect. Conveniently, the paranormal creatures (all men) didn't want to the heroine to know what they were, how they worked, what their mission was. (One of their kind had strayed from the path and was keeping humans in thrall. Why? I have no idea. Didn't get to that part if it was ever explained.) But the author kept the reader in the dark, too, even though we were in male POVs quite a bit.
From what I gathered, the hero was of a race that I think lives forever. (That's a good thing, I suppose, since I neither heard of nor saw any females of that race.) The males could have meaningless sex with human females or relationships doomed to die because of the male life expectancy. That was the conflict. It's a good conflict, but again, I never cared that much about the characters. The paranormal guys' dialogue sounded stiff without the use of contractions, and slightly patronizing. I got the "We are superior beings and you wouldn't understand" vibe from them.
The hero was less so, but still for some reason, I didn't quite buy the relationship between the him and heroine being anything more than sexual. I've tried to figure out why, but can't put my finger on it. The author certainly showed them both displaying admirable qualities. The hero saves the heroine's sister from a fate worse than death. But for some reason, when they are forced to part ways about one third of the way in, I didn't much care.
Now, that fate worse than death... Sis was held captive and in thrall for several days by the villain. I never found out what happened to her. Maybe it was explained later. But Sis didn't want to talk about it and/or couldn't remember what happened. I'm a little fuzzy on which. It didn't help that Sis was pretty one-dimensional. She was a weak Miss Perfect Sunshine woman who probably never farted.
So, upon reflection, I suppose that the biggest reason I gave up on the book was the lack of information about what was going on and what had happened but wasn't explained. It's good to have the reader asking questions. They read to get those questions answered. But when you hold out on the answers too long, the reader may get tired of or frustrated with waiting. And when you add a romance relationship that has no chemistry beyond the sexual and a hero you're not in love with yourself, you get a DNF book.