From this page anyone can download free PDF files of “digital second editions” of the four books of mine whose first editions were published in the Cornerstones series of Birkhäuser Boston between 2005 and 2007. These books are at the first-year graduate level or a little higher, depending on one’s university. Two of the four are available for download now, and two are to be available later in 2016, as follows:
Basic Algebra (available now)
Advanced Algebra (available now)
Basic Real Analysis, with an appendix “Elementary Complex Analysis” (available later in 2016)
Advanced Real Analysis (available later in 2016).