I first read Sword of Shannara and it took some time and some re-reads to be hooked. This book was different. Both Sword and Elfstones continue a series of themes that can best be explained as, "Use your brain and not your sword," and "The weak can be powerful if they are determined and principled". Brooks' characters are forced to confront themselves BEFORE they can effectively solve their problems. I have always loved this psychological addition to the genre and Brooks does it better than anybody. However, the density of this task often bores people. I don't think Elfstones had this problem.
While Elfstones has the above themes, it also is highly successful as an exciting, page turning (no, page ripping) flight of fear and desperation. Any Brooks fan is likely to tell you this is his finest work. It is a rare book that can give you the depth of character and boiling action to satisfy both branches of our fantasy-fan brethren.
While I hold Tolien on a different plane, Elfstones is perhaps the book that most -approaches- the level of excitement and depth of the Lord of the Rings. And in addition, it is much less derivative than other books (but some derivation is unavoidable).
Here is my advice: Read the Sword of Shannara first. It is the best introduction to this world written and should not be avoided. But while you are reading Sword keep this in mind - all the work will pay off in that a ripping adventure is waiting for the informed in the form of Elfstones.
It is an adventure that will make your heart beat, make your hair raise, and ultimatley make you cry. So deeply did I care for the two main characters that at the end I had trouble accepting it, though I knew there was no other solution within the principles of the actors. Yes, I mourned a bit.