Volume 4 of Pokemon Black and White contains chapters 11 to 13. It is rated A for all ages. (although it obviously contains some violence) I would recommend reading the previous volumes before reading this one.
Volume 4 starts with Black chasing his Munna but he ends up fainting. When he wakes up, White is with him in a laboratory owned by Professor Fennel and her assistant, Amanita. It turns out that Professor Fennel went to university with Professor Juniper. The four of them search for Black's Munna but find it captured by Team Plasma! Also, whilst filming, an accordion is stolen from the set. Black is blamed but by using Munna, he proves that is wasn't him. And Black begins his battle with the Nacrene City Gym leader, Lenora!
Not as good as the previous volumes. It kind of turned into a detective series where Munna helps Black solve problems at the start, but the final chapter made up for it with Nacrene City Gym battle finally starting! The next volume should be better with hopefully more battles.
The cover of the book has a weird texture. I'm sure the other volume weren't as uncomfortable to read as this one. The squares on the cover have different textures. The black/white squares are smooth but the grey squares are rough. The book is really thin though so it's not like you will be holding it for a long time. Like the previous 3 volumes, it isn't the same size as a regular manga volume, it's shorter yet wider.
Overall, for the price it's a good buy. Not great but it looks nice in any manga/Pokemon collection.