Halsey: Assuming you mean a first Titanic book, I'd have to recommend Walter Lord's "A Night to Remember". It's the definitive "mother of all Titanic books" and the one that sucked most of us into this particular vortex. ;^)
If you're looking for a 1912 contemporary, first-person perspective, both Lawrence Beesley (a 2nd Class Passenger) and Colonel Archibald Gracie (1st Class) wrote personal narratives at the time that are really stunning work. (Walter Lord himself relied heavily on both for some of his information.)
All of the above (in various formats) are pretty widely available through Amazon.com, Barnes and Noble [B&N.com], and various discounters. Colonel Gracie's account (originally titled "The Truth about Titanic") is also available in combination with Jack Thayer's later reminiscences, in a dual publication entitled "Titanic: A Survivor's Story". (For a teen especially, Jack's recollections are very poignant; he was only 17 at the time of the disaster, and lost his father as a result.)
Short of reading the Inquiry transcripts per se, it's pretty hard to get any closer to those events from an eyewitness perspective. And though some of the technical details were ultimately incorrect -- both Gracie and Beesley, for instance, believed the ship went down intact -- there's nothing quite like that feeling of "being there". (Of course, Walter Lord also conveys the impression splendidly, even though he wasn't there.)
P.S. If you pursue "A Night to Remember", keep in mind that the widely available (and very reasonably priced) "mass market paperback" [Bantam?] omits the Index that's present in other editions; there are a few complete ones out there, most easily located online, though they cost slightly more. (None of the contemporary accounts were ever indexed.)
Let's not forget Titanic, Triumph and Tragedy also by Eaton and Haas. This is also readily available through most of the on-line booksellers.
As to the Inquiries, you can click on Titanic Inquiry Project for the complete transcripts of both the British and U.S. investigations as well as the reports. This is one you should bookmark. You can get the hardcopies, but the things are rather pricy !$!$!$!$!$!$
While seconding all of the above suggestions (particularly Walter Lord's 'A Night to Remember'), I'll also suggest Don Lynch's 'Titanic: an Illustrated History'. The books by Lord, Eaton & Haas, and Lynch are readily available where you are and you should be able to borrow them from your library if buying books isn't really an option.Try to get the second edition of the Eaton & Haas book, though, as it corrects a few things that slipped into the first edition.
From your comments in another thread you're clearly capable of reading and enjoying full length books, so I'm not going to suggest and books written specifically for younger readers. However, another book you may find interesting is 'The Complete Idiot's Guide to the Titanic' by Jay Stevenson and Sharon Rutman. Don't let the title put you off: it's engagingly written and covers Titanic history through to salvage and Cameron's film. I'm suggesting a look at this one as it's definitely one of the more popular books with the teenagers who use my library. Yes, there are some factual errors, but the same can be said for several of the books suggested above. And if you've read Lord, Lynch and Eaton & Haas you'll start spotting discrepancies and questioning what is and/or isn't fact, which will set you up as an Titaniac with an enquiring mind for quite some time.
There are several other threads in this book forum where recommendations are made and the suggested books discussed. I hope you find them useful.
I pretty much agree with all of these suggestions, you won't go wrong with any of them. Halsey you didn't say how old you are, and "teen" covers a wide range. I would recommend very different books to a young teen as opposed to someone in their late teens.
for a truly awesome read, a book that is just so good you can't put it down, by far Walter Lord's A Night to Remember is still one of the best. after that, a more in-depth telling of the story, which is also a tremendous read is Geoffrey Marcu's The Maiden Voyage, though this one would be best for an older teen I would think.
if you want lots of pictures to go with your words, Don Lynch's Titanic, An Illustrated History is the best of the batch. and although it has some bloopers in it. I personally thought Leo Marriott's Titanic was a great blend of images and words.
finally, if you are not too young to appreciate a kid's book, as far as pure imagery goes, you can't beat Steve Noon's Story of the Titanic.
the really good news is that once you get started, there are enough books on the subject to just about last you a lifetime. happy reading!