There are many bad arguments against immigration and this book takes a stab at countering them with science and reason. It covers a lot of ground in an interesting format and is well worth a read.

I think it has a couple of flaws though. Unsurprisingly, considering Caplan is a professor of economics, the book relies heavily on economic arguments and GDP as a yardstick. Surprisingly, considering Caplan's use of the "if all you have is a hammer, everything looks like a nail" argument against solving potential problems deriving from immigration by limiting immigration, the book shows little awareness of the shortcomings of the analyses used as arguments. Sure, we can extrapolate a lot from available data, but Caplan sort of leans on a "not everyone will want to or be able to get here, so the numbers wont be extreme"-argument to avoid thinking of the limits of extrapolation. And GDP and judging everything in the terms of economics have some serious shortcomings.

I would also have loved if the book included at least a mention of "The Science and Ethics" of the forces driving immigration. When talking about "keyhole solutions" Caplan suggests taxing immigrants harder to compensate for them "getting services they haven't paid for", (It's not as bad as this summary makes it seem, you should read the book.) and similar, but what about the ethics of outsourcing our production to people who aren't given the right to a safe working environment? Is opening our borders to them really the keyhole solution? With a subtitle like "The Science and Ethics of Immigration" I think those aspects should have been given at least a little space, even in a book on Open Borders.