Late in August, the text originally selected for my mathematical logic class became unavailable. On the basis of reviews only, I chose Mendelson's Introduction to Mathematical Logic as the replacement. A disasterous choice. There may be a page without a typo, but I don't expect to find it. The presentation is inconsistent in notation and focus. Concepts are confused and more difficult than they should be. Definitions are not wisely selected. This book reads like something that has been patched for four decades (since 1964). On the positive side it contains interesting supporting material and will be a valuable private source of ideas to the lecturer. Be sure to read sections from chapter 2 and 3 before selecting this as a text.