Reddit mentions of Understanding Syntax (Understanding Language)

In regards to the third question, there are generally considered to be five kinds of relative clause, in a hierarchy.

In order:

1. Subject
   
2. Direct Object
   
3. Object of an Adposition (preposition/postposition)
   
4. Object of a Possessive Noun Phrase
   
5. Object of a Comparison
   
   The idea is that if a language can relativise a lower position on the list, then it will definitely work for a higher one - for example, if you can say "The table which I placed the cat under" (Position 3, "under" is a preposition), then you must also be able to say both "The plate which fell" and "The plate which I dropped" (Postions 1 and 2, respectively), but not necessarily "The man whose friend won the book" or "The sword which my knife is sharper than" (Positions 4 and 5).
   
   This book has some good info on relative clauses in it, and I know for a fact that there are free pdfs of it floating around the internet somewhere if you look for them.
   
   I also wrote a short essay last year with several examples of each kind of relativisation, comparing how relative clauses work in English with one of Tolkien's Elvish languages and Irish (all the examples are translated into English :) ), if you'd like to have a read.

Maggie Tallerman is a syntactician who has written some intro level books to syntax. When I was an undergrad, I read her book Understanding Syntax for an Intro to Syntax course. It looks like a new version is coming out this September: http://www.amazon.com/Understanding-Syntax-Hodder-Education-Publication/dp/1444112058/ref=sr_1_1?ie=UTF8&qid=1312761900&sr=8-1