Exclusively about the plot, the book that pictures the events after the 10th episode of the 2nd season would be A Storm of Swords, the third book of the series.
The issue is, if one reads the third book without reading the first two, one would be confused, specially regarding some characters of the books whose parts have been condensed or combined into different characters. The books have a lot more characters than the series.
So, the best would be to start reading from the first book. You would recognize the main scenes, and would understand what was going on in the minds of the characters, as well as getting to know some of the characters that didn't appear in the series.