Welcome. The following are some good books. They are in no particular order other than from left to right on my shelf. I would recommend looking through the forum. There is a ton of information here.
Pro Ufology Books
Flying Saucers and Science: A Scientist Investigates the Mysteries of UFOs (Friedman, ISBN: 1601630115)
Witness to Roswell (Carey/Schmitt, ISBN: 1601630662)
Dimensions: A Casebook of Alien Contact (Vallee, ISBN: 1933665289)
Messengers of Deception: UFO Contacts and Cults (Vallee, ISBN: 097572004X)
Revelations: Alien Contact and Human Deception (Vallee, ISBN: 1933665300)
Confrontations: A Scientist's Search for Alien Contact (Vallee, ISBN: 1933665297)
UFOs: The Great Debate: An Objective Look at Extraterrestrials, Government Cover-Ups, and the Prospect of First Contact (Danelek, ISBN: 073871383X)
Left at East Gate: A First-hand Account of the Rendlesham Forest Ufo Incident, Its Cover-up, and Investigation (Warren, ISBN: 159605753X )
The Cryptoterrestrials (Tonnies, ISBN: 1933665467)
Dark Object: The World's Only Government-Documented UFO Crash (Ledger, ISBN: 0440236479)
On the Trail of the Saucer Spies: UFOs and Government Surveillance (Redfern, ISBN: 1933665106)
Classic Reading
The Flying Saucers are Real (Keyhoe, ISBN: 1450514618)
Firestorm: Dr. James E. McDonald's Fight for UFO Science (Druffel, ISBN: 0926524585)
The Report on Unidentified Flying Objects (Ruppelt, ISBN: 1606802534)
Pale Blue Dot: A Vision of the Human Future in Space (Sagan, ISBN: 0345376595)
Opposition Books
Why People Believe Weird Things: Pseudoscience, Superstition, and Other Confusions of Our Time (Shermer, ISBN: 0805070893)
The Skeptic's Dictionary: A Collection of Strange Beliefs, Amusing Deceptions, and Dangerous Delusions (Carroll, ISBN: 0471272426)
Pseudoscience and the Paranormal (Hines, ISBN: 1573929794)
Paranormal Claims: A Critical Analysis (Farha, ISBN: 0761837728)
Skeptoid: Critical Analysis Of Pop Phenomena (Farha, ISBN: 1434821668)
The Skeptic's Guide to the Paranormal (Kelly, ISBN: 1560257113)
Things and people to be weary of (not a complete list. just ones off the top of my head.)
Dr. Steven Greer
Stan Romanek
Richard C. Hoagland
Roswell
Drones
Richard Dolan (I know, but it's how I feel)
Whitley Strieber
Eric Von Daniken
Area 51 Specifically the "S4 Complex"
Bob Lazar
Majestic 12
Project Camelot
Alien-Human Hybrids or Paracast Sponsors who project that title onto a person after knowing them less than a day and with no real proof.
Clifford Stone
Michael Serrada (or however you spell it)
Jim Marrs
John Leer
Movies starring Kate Blanchett, Billy Zane, Shirley Maclaine, or Rutger Hauer (not UFO related but sound advice none the less)
OR.... you could could find another hobby. I'm not trying to be a jerk with this. This subject seems to consume people at times. At 19 i am not sure how susceptible you are to that sort of thing. Hell, at 19 all I cared about was girls, food, girls, school, girls, and girls. Anyway, I make no bones about telling people not to get interested in this subject in any depth. I would offer you the same advice. Believe me there are better things you can do then look into this stuff. I wish I had someone that would have convinced me of that years ago before I got so caught up. Anyway, if you decide that this old fat guy is just too cynical and jump in with both feet anyway then at least your trip to insanity will be well paved if you read the books listed and be weary of those things. Good luck in whatever you decide.