It is an old book. It was a great book at the time but computing is a rapidly changing field. A used copy of the first edition can be had at a reasonable price.
It's hard to characterize the state of compilers in 2017. In the 1980s there was real innovation in the commercial space with things like Turbo Pascal. Then the market for cheap compilers got squeezed out by GCC, Microsoft, Intel, etc. Apple got behind LLVM and made it viable. In the meantime a lot of dynamism got behind Java, Python and other systems with more dynamic runtimes.
There are many exciting developments in compiler technology but they do seem to me to be fragmentary and not yet put together into the makings of (say) a great textbook or a framework which would put compiler technology into the hands of many more people.
One of the things that I did notice in the 2nd edition is its preference to cite GCC in references.
Back in 1990, students in an OS class might be doing pretty well if they manage to get something that boots. Writing a compiler from scratch is also pretty tough.
Today students can write device drivers for Linux as well as other modules, also hack on open source compilers.
I think the same thing could have been said back in 1977, and the dragon book pulled all of these things together. What's needed is someone today doing the same kind of thing with current technology. (Publishers, if you are reading and think there's a market contact me ;-)