The student who is aspiring to participate in the International Astronomy Olympiad may find the following books very helpful while preparing for the examination. In any case, if the student wants to get the basic knowledge of astronomy then he or she might refer to the Astronomy: Principles and Practice Fourth edition by A.E.Roy and D.Clarke. The most recommended textbook for astronomy which is very well written and is recommended by everyone to a candidate to start preparing for the IAO examination is The Universe by the authors Roger Freedman, Robert Geller, and William. J. Kaufmann.