*Oscar Levin writes to share news about his open discrete math text:*

After many years of development, I am pleased to announce that the 4th edition of *Discrete Mathematics: an Open Introduction* is now available, on the both the book’s home page and on Runestone Academy.

The 4th edition brings many improvements and a new organization of content. In particular, the book now starts with logic and proofs, then practices those proofs with graph theory. The second half of the book contains material on counting (with a new “application to probability” section) and sequences. Over the last few years, I have found that students have more success with this arrangement.

The new edition contains more interactivity as well. More interactive exercises (which you can give students credit for if you create a course with the book on Runestone Academy; it is completely free for you and your students) and some interactive Sage and Python code to explore some topics.

There is not currently a print version of the 4th edition. Some time in the next year, CRC will publish the physical version, but the online versions will remain available and free forever.

The third edition will also remain available indefinitely.