I'm looking for novels on paperback that have 7 or more volumes. Any genre.
Looking at your list, these might be of your interest:
-Overlord (noticed you're watching the anime, but the LN goes way more in-depth obviously)
-Grimgar of Fantasy and Ash (only 4 of the 13 volumes translated and on paperback though, bookwalker has until volume 9 in digital format)
-Goblin Slayer (also has a LN, besides the manga, but only up to volume 4 released)
You can also find the digital editions for these LNs on Bookwalker.
Log Horizon is available and will have up to volume 11 out in January (in which we will actually be caught up to japan release wise) (author plans to have have at least 16 books)
Sword Art Online will have up to volume 15 out in December (currently at 20 books)
Baccano! as of the 21st will have volume 8 (22 book series)
Durarara!! has 13 books for the first series but we only have up to volume 10
Accel World will have 15/22 books in September
A Certain Magical Index will have 17/22 books in November
Mushoku Tensei it's technically a web novel but it has the same structure of a light novel. 30+ volumes, recommended for a long read