[quote=@OneStoryToMany]
[@PKMNB0Y] Are they books? And I will, if they really are any good.
[/quote]

Manga and light novels; light novels are further along. Both have an anime, but I'd only recommend Log Horizon season 1 since the animation for season 2 was done by DEEN and it detracts heavily from the good points of the series.
Overlord's on volume 9 in terms of light novels, but since it's been licensed the last writer (Skythewood) has since dropped his translation efforts.