I was trying to find a couple of books I read as a kid, and could not.
I will try and sum up the points I remember about them, and please try
and find out the title and author.
BOOK 1:  A science fictiony book I read in about 5th grade (Im now
27). Its about a boy who finds a shed that can stop time. He wanted to
be different from his brother (twin) and decides to stay in it for a
year to be a year or so older than his bro. It actually slows down
time he figures out. He has a schedule worked out that allows him to
pass the time, pushups, reading novels, etc. He has a clock or watch
that ticks very slowly. In the end, some creature crawls up through a
drain, and eats itself. He runs naked through the woods in 'real-time'
a few times and almost gets caught.
BOOK 2: I remember even less about this one.  It had to do with
dimensions, and being able to look into the fourth dimension. It was
hard learning to look at things in thei dimnesion, and to scan a room,
meant looking on different planes, etc... very confusing. The two main
characters found ultimately that infitive dimensions existed, and
looking the other way into 2 dimensions he saw like paper cutout
people living, etc.

please let me know if you have heard of one or both of these books.
Maybe by the same author, but prob not. My librarian was trying to get
me interested in reading, and these really stuck with me.

- Book 1 -

The first book is without any doubt: "Singularity", by William
Sleator. Here is a brief excerpt from a description I found; it shows
clearly that this is the book you remember:

"Singularity is the story of twin brothers who, during a summer
tending their late uncle's home, discover that the old man built a
shed to enclose a singularity, a place where time flows much faster
then normal. The "younger" twin, feeling dominated by his stronger
twin, sneaks to the shed one night and lives a full year in complete
isolation -- overnight. He emerges the next morning inches taller and,
more importantly, much wiser."
Source:
Hatrack River: Books to Look For
http://www.hatrack.com/osc/reviews/f&sf/88-08.html

"Singularity" is currently in print and available in the USA, for
example from Amazon ($5.99):
http://www.amazon.com/exec/obidos/tg/detail/-/0140375988/102-0783463-4014520


- Book 2 -

Concerning the second book, it's much harder to provide a definitive
answer. Many novels dealing with 2-dimensional worlds and higher
dimensions than our own have been written since Edwin A. Abbott
published his "Flatland: A romance of many dimensions" in 1884. By the
way, you can read that Science Fiction pioneer  novel online here:
http://www.alcyone.com/max/lit/flatland/
(Source: Erik Max Francis' Homepages)

However, I finally came to the conclusion that the book you remember
is most likely another novel by William Sleator, "The Boy Who Reversed
Himself". The main idea of that novel is that apart from our
3-dimensional world, there is not only a 2-dimensional one, but also a
huge number of higher dimensions. Here are some excerpts from reviews
to give you an impression of the plot:

"In it [The Boy Who Reversed Himself], a young boy [Omar] can "move"
into 4 dimensional space.  By doing so, he can move in between objects
in 3-D space. He can now walk through walls and travel any barrier in
3-D space. In 4-D space, he can move into new directions, called ana
and kata. The idea is, their are "keepers" of every dimension, who
make sure that everything is "o.K."  The keeper is from the succeeding
dimension.  For example, the person from 4-D space watches over 3-D
space, and a person from 3-D space watches over 2-D space.  The boy
was being groomed to be the new "keeper" of 2-D space by his
"grandfather.""
Source:
Astronomy 102 (Black Holes and Quasars) Student Discussion List,
January 6 to January 21
http://www.astro.washington.edu/bbeck/102/discussion/jan06-jan21.html

"When Laura finds her homework in her locker with its writing
reversed, she's baffled until she learns an unbelievable secret--her
weird neighbor, Omar, has the ability to travel to the fourth
dimension. Laura forces him to take her there and then, a novice in
"four-space", she goes out there on her own. There's only one
problem--she doesn't know how to get back."

"She [Laura] has a crush on Pete, the football captainand weird things
are happening on a daily basis, ever since Omar, the creepy boy next
door, moved in. Laura makes Omar confess his secrets: he's training to
become the guardian of the Second Dimension, while he's exploring the
Fifth. Laura invites Pete on a journey to the Fifth Dimensionbut her
game becomes a nightmare when she and Pete are captured, and the whole
existence of the world depends on Omar's ability to rescue them."
Source:
Amazon.com editorial reviews of the book
http://www.amazon.com/exec/obidos/tg/detail/-/0140389652/102-0783463-4014520?v=glance&s=books&vi=reviews

I am quite sure that this is the book you have in mind. It, too, is
available from Amazon for $5.99:
http://www.amazon.com/exec/obidos/tg/detail/-/0140389652/102-0783463-4014520



Sources:

Manchester Township School District: Reviews Science Fiction
http://www.manchestertwp.org/reviews_science_fiction.htm

Surpriced.com: Singularity
http://book.surpriced.com/0140375988.html

Xavier University: Home Page for Dimensionality, Spring 2004
http://cerebro.cs.xu.edu/~smbelcas/dims.html

Future Technology: Dimension, by David Cary
http://www.rdrop.com/~cary/html/dimension.html

Abebooks: BookSleuth - Recently Solved
http://www.abebooks.com/docs/ReadingRoom/BookSleuth/Solved/solvedApr9.shtml

The Christian Science Monitor: Personal Accounts and Folded Paper
http://search.csmonitor.com/durable/1997/10/03/feat/scitech.1.html


Search terms used:
"older than his twin" "science fiction"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22older+than+his+twin%22+%22science+fiction%22&btnG=Google+Suche
Sleator singularity
://www.google.de/search?q=Sleator+singularity&ie=UTF-8&oe=UTF-8&hl=de&btnG=Google+Suche
Sleator singularity twin
://www.google.de/search?q=Sleator+singularity+twin&ie=UTF-8&oe=UTF-8&hl=de&btnG=Google+Suche
attic boy "fourth dimension" "two dimensional"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=attic+boy+%22fourth+dimension%22+%22two+dimensional%22&btnG=Google+Suche
"william Sleator" "two dimensional"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22william+Sleator%22+%22two+dimensional%22&btnG=Google+Suche
"The Boy Who Reversed Himself"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22The+Boy+Who+Reversed+Himself%22&btnG=Google+Suche
flatland
://www.google.de/search?q=flatland&btnG=Google+Suche&hl=de&ie=UTF-8&oe=UTF-8&newwindow=1
"boy who reversed" dimensions
://www.google.de/search?q=%22boy+who+reversed%22+dimensions&hl=de&lr=&ie=UTF-8&oe=UTF-8&newwindow=1&start=20&sa=N


Hope this will help!
Best regards,
Scriptor

Great !!! You are correct. Ordered the books, and they came today.
Thanks for letting me re-experience some books that have stayed with
me since I was a kid.

Great work, scriptor. They're available used too, for $1.00 or so -

http://www.bookfinder.com/search/?author=Sleator&title=singularity&new_used=*&binding=*&isbn=&keywords=&minprice=&maxprice=&classic=on&submit=Begin+Search&currency=USD&mode=advanced&st=sr&ac=qr

http://www.bookfinder.com/search/?author=Sleator&title=Boy+Who+Reversed&submit=Begin+Search&new_used=*&binding=*&isbn=&keywords=&minprice=&maxprice=&classic=on&currency=USD&mode=advanced&st=sr&ac=qr