Just buy the first issue digitally. It's cheaper and is the main reason why anyone reads Gotham by Gaslight (The second issue has a different artist and isn't as fun as the first).

The first issue is a quick read at just 50 pages and doesn't have as much Batman as I expected it to (he's Bruce Wayne for most of the story). This interpretation of Jack the Ripper also feels very different from the historical figure, but hey, it's Batman vs Jack the Ripper, what'd you expect? It's a fun premise and a decent little mystery that can be finished in an afternoon. The art is really great too. Mike Mignola's art is very gritty and uses a lot of harsh shadows. It's perfect for a story like this in Victorian era Gotham. Not the greatest Elseworlds story I've read from DC, but still pretty fun.