Mortal Instruments by Cassandra Clare or Nightshade by Andrea Cremer. Which
book is it? The first? Second? Often the number isn't listed on the book.
That's where Fantastic Fiction comes in. This is a terrific
site that clearly lists all the books in any series. You can search by
author or book. It also lists all the future books in a series that will be
published in the next couple of years.
Go to Fantastic Fiction and
look for your favorite author.