Two short novels, written as if they were a series of blog posts, about a college student and his older fujoshi girlfriend (she's way into anime and manga, particularly BL stuff). If you like good romance, playful banter, and references to otaku culture, this is a great pair of novels.
The bulk of the humor involves the playful banter between them, as she slowly drags him down the otaku path, while he actively resists it. They are constantly teasing each other, but do so in a fun and loving way--and some of the MC's observations about his girlfriend are absolutely hilarious.
drop references to a huge number of anime and manga--some of which are explained, and some of which aren't. I wouldn't recommend this to anyone who wasn't reasonably familiar with a wide swath of otaku culture already. If you are familiar, however, the references are sometimes clever and often funny.
But at the end of the day, the characters really do love each other, and that's what I appreciated most about the novels.
Compared to the manga, there are some differences. Their are very few side-characters mentioned, and none for very long. The MC's best friend is only mentioned a couple times. He doesn't have an otaku sister. And the whole bit with the girl's boss is missing entirely. On the other hand, their are plot arcs where they meet each other's parents, which are great. And the end of Vol 2 gives the satisfactory resolution that you wanted from the manga but didn't get.