Q:

Are "recommend me" questions allowed? 

Are questions of the form "I really liked X series.  Could you recommend me some similar works?"  allowed? 

A:

Actually, there are guidelines: the site definition questions.  And based on the votes there, I'd say that recommendations are on topic here. 

A:

Should definitely be allowed.  It's very common for people to enjoy a relatively exotic sub-genre of sci-fi and having a hard time finding similar novels.  The niche aspect of some sub-genre makes word of mouth the best way to discover new gems. 

A:

Quite frankly, I use a very large number of the questions as the "recommend-me" questions to some extent. 
For example, in https://scifi.stackexchange.com/questions/130/what-are-the-most-common-ways-of-communication-between-humans-and-aliens besides satisfying my curiosity also gave me a list of interesting books to read. 
As another example, https://scifi.stackexchange.com/questions/7/has-any-science-fiction-work-accurately-predicted-the-emergence-of-future-technol is probably the best question I've seen on this site (just my humble opinion).  And, surprise surprise, it contains a nice list of interesting works, each one implicitly being a recommendation. 
This site is a great place for science fiction enthusiasts to recommend things to each other, and to be completely honest, I don't see a problem with that!