The Transactions XXVIIIA Reports on Astronomy 2010-2012 provides a comprehensive and authoritative review of what has been achieved in astronomy during the years 2010-12. These insightful and up-to-date reviews from the IAU Divisions and Commissions have been written by the presidents and chairpersons of the IAU scientific bodies. Topics covered in this wide-ranging volume include: fundamental astronomy; the Sun and heliosphere; planetary sciences; stars; variable stars; interstellar matter; the Galactic system; galaxies and the Universe; optical and infrared techniques; radio astronomy; space and high-energy astrophysics; and other IAU activities. The reviews have been written at a level suitable for colleagues in the same fields, but will also be useful for students and researchers wishing to gain an overview of astronomical fields beyond their own research area.