[Borek]

So, this is one of those "how do you call it in English" questions of mine

When you study you use a textbook. Textbook may contain questions.

But how do you call a book that contais only questions?

[sjb]

I don't really think it has a special name as such, perhaps a "workbook" or something? What's the Polish (or German) term - not that I speak Polish mind...

[Borek]

In Polish it is "Zbiór zadań" - "zbiór" means set (in math) or collection (I have a small collection of Warsaw postcards), "zadanie" is either task or question (so if someone from Poland will ask for help in solving a task, you will know what he is talking about ).

"Zbiór zadań" sometimes contains only questions, but it can contain also some introduction to the methods used. Basically not general theory, just ways of applying laws and formulas. Sure, there are no precise rules about what is called "Zbiór zadań".

[Mitch]

supplementary materials

[Yggdrasil]

I'd call something like that a workbook or problem book.

[enahs]

If it is a companion to a specific text book, "Study Guide".

And even if it is not a specific book, but a type of book with the general same theme.
Example, I would call this a "Study Guide":
http://www.amazon.com/Schaums-Outline-College-Chemistry-Outlines/dp/0071476709/
It is mostly Questions, and can be used with any General Chemistry book.

[Borek]

Thank you all. I feel like problem book is the closest; but that's just my humble feeling.

Funny thing, how sometimes things or concepts that have a simple and established name in one language, in other language require description because such a short name doesn't exist.

I have followed link that Enahs posted and between other similar books "3,000 Solved Problems in Chemistry" of Schaum's Solved Problems Series was listed. In Polish it will be most likely called "Zbiór zadań z chemii" - you should be easily able to guess what it does mean