Modern Architecture: A Critical History by Keneth Frampton
Architecture and Disjunction by Bernard Tschumi
Delirious New York by Rem Koolhaas 
Complexity and Contradiction in Architecture by Robert Venturi
Toward an Architecture by Le Corbusier
On and By Frank Lloyd Wright by Robert McCarter
The Eyes of the Skin: The Architecture and the Senses by Juhani Pallasmaa
and many many others...

Start out with some light reading:

Sanford Kwinter, Architectures of Time: Toward a Theory of the Event in Modernist Culture (2001)

Since there are only histories of architecture (and no definitive history), If you wanted to start with the big picture from various viewpoints, I would suggest the following:

Kostof's "History of Architecture"

Frampton's "Modern Architecture: A Critical History"

Banham's "Architecture and Design in the First Machine Age"

Rand recommended tough reads for a amateur in my opinion. Those are books you will start getting into once you are in school. 

If you want History, you want Kostof:

A History of Architecture: Settings and Rituals by Spiro Kostof

The City Shaped by Kostof should be on the list as well. I’m not so sure it will be a bit heavy for starter, albeit really good one to read.

Also some other good read are Invisible Cities by Italo Calvino and The Image of the City by Kevin Lynch.

Try Michael Sorkin and Witold Rybczynski- accessible and interesting writers.  I am in the process of reading Deyan Sudjic's The Edifice Complex: How the Rich and Powerful Shape the World and like it a lot so far. Mario Salvadori has a couple of good books on structure written for the layperson.

"A History of Western Architecture" by David Wadkin.

Don't read anything, just watch "my architect" and you'll be good to go.

History of Architecture by Kostof. Read it, if you like it then you can apply for an Architecture course.

the fountainhead.  That's so realistic some people think it's non-fiction.  Also, at some point in your college education a professor will refer to Howard Roarke.  Might as well know who he is.

I recommend the Wikipedia page f the fountainhead. You will understand all the references people make without wasting the time or developing the the misconceptions created by the book (you will probably just develop them from somewhere else though).

They still make encyclopedias? 

I think the printed encyclopedia may be a thing of the past:

http://abcnews.go.com/blogs/technology/2012/03/encyclopaedia-britannica-kills-its-print-edition/

However, wikipedia does have a page for starchitects:

http://en.wikipedia.org/wiki/Starchitect

The importance of knowing and aspiring to be a starchitect far exceeds any other knowledge you can have on architecture.

I just read Kengo Kuma's "Small Architecture, Natural Architecture." 

I highly recommend the two books. You can order an English copy of the book through the AA bookstore. The books aren't very thick, they go through architectural theory just as much as it does practicality in building...

read all the books suggested here and you will have read more theory books than many graduating from university xD