Translation:Dictionaries are not thin.
The form with ありません is very formal. ない is a lot more practical and common.
In Chinese, 細 is similar to slender. It can be used to describe a 0.5mm ball point pen. You can always find this character on the packaging of ballpoint pens or pencils made in Japan. In comparison, 薄 is similar to thin in terms of the materials. It can be used to describe a thin piece of paper, clothes, or cakes etc.
Report it, it's exactly what I put, and means exactly the same as "Dictionaries are not thin".
I love how I can fit every dictionary I ever need on a thin smartphone though.
細い is thin for hair, a line, a rod, a lane - something that's long
薄い is thin for clothes, paper - something flat
Is it common to describe books as "thin" or "thick" in Japanese? It sounds kinda weird to use those words in English, I'd be much more likely to say "short" or "long"
If all the pages were blank, would you still call it long? When you tall about long (or short) books, aren't you really talking about the comments of the book? Also, if the book consists of sections that are unrelated to each other, so that no section of the book is long on its own, would you still use "long" to describe it?