The Last Days: 70 A.D.

Here's the best and most succinct book explaining what the New Covenant Scriptures mean when it speaks of the "great tribulation", the "end of the age(s)", and the "last days". It is entitled The Great Tribulation by David Chilton.
Here it is on Amazon
Here's the whole book in PDF format

Another that I learned much from years ago that I still heartily endorse is by R.C. Sproul, Sr. entitled The Last Days according to Jesus: When Did Jesus Say He Would Return?

Finally, Joel McDurmon of American Vision has written an article that covers alot of End Times ground.  I commend this article to all those who tend to think that all that last days, eschatological "stuff" the Scriptures refer to just can't be understood.  It can!  But you must commit yourself to reforging your way of understanding the World and Knowledge.  This can only happen through renewing your mind in the Bible's view of covenant and symbols and types and of thinking.  Very strange to our modern mind, and very uncomfortable to confront for most believers.  

His article will help.  Here it is:  What is the Last Days