I think this depends on your requirement for font sizes.
Just download the free sample (can even be done from your Kindle device) and flip pages until you arrive at the first pictures. For me they are quite small, but large enough to read the text. You can also select the pictures to view them full screen.
Another way of reading this is not buying it at all, but converting the web pages. This can be done for example using the grabmybooks browser extension. Note that it relies on Calibre for the conversion from
.mobi. The result looks similar to the book for me.
I may add that the latter way did not always work well. In the past I had problems with pictures missing or being black. Now it works, but I cannot say if this is due to bugfixes in grabmybooks or Calibre or if xkcd used another image format (or version) in the older articles.