Scroll:
The scroll is considered to be the first book form. Scrolls are made from 2 layers of papyrus pith (the central cylinder of the stem) which are laid at right angles to each other then pounded together. The sugar in the sap of the plant then binds them. Individual sheets were overlapped and pasted together using a flour and water paste to form a long roll or Charta. Parchment, made from animal skin, was used as an alternative to papyrus.
Developed by the Egyptians, papyrus was used as the main writing material in the ancient Greco-Roman world. It was exported to other parts of the world, but the dry environments in
Papyri were used as widely as contemporary texts and were for public and private use. Texts have been found on diverse topics such as religion, taxation, administration, marriage contracts, literature and horoscopes.
The main reasons papyrus remained the main writing substrate was because it was reasonably cheap and easy to produce. Although parchment was used, it was difficult and more expensive to produce and so didn’t take over from papyrus until the wider adoption of the codex form.
“The roll was stored upright in a book-box or capsa, horizontally on a shelf or in a pigeonhole. If particularly valuable, it could be placed in a chest or wrapped in a protective sleeve of parchment and tied with thongs. An author's work very often would require several rolls, which would be kept in the same book-box. It was these physical limitations--the length of the papyrus roll and the number of rolls that could be stored together--that tended to define the divisions of literature.”http://penelope.uchicago.edu/~grout/encyclopaedia_romana/scroll/scrollcodex.html
“…constantly being unrolled and rolled back up again caused abrasion and, even though writing only on one side of the page reduced the problem of wear, it was inefficient and made the roll that much more cumbersome to store. Author and title were indicated at the end of the text (colophon) and so were less vulnerable to damage when the roll was rewound, but this made it more inconvenient to identify the contents (there was a tendency, too, for the titulus to fall off). Since the individual sheets of the roll were seamlessly joined, lines and columns were not uniform but varied in length and size. Nor were they marked, which made citation difficult and often inaccurate.” http://penelope.uchicago.edu/~grout/encyclopaedia_romana/scroll/scrollcodex.html
References:
http://www.csu.edu.au/faculty/arts/humss/art317/form/briefhist.htm
http://scriptorium.lib.duke.edu/papyrus/texts/world.html
http://www.wordwebonline.com/search.pl?w=parchment
http://scriptorium.lib.duke.edu/papyrus/texts/rule.html
http://penelope.uchicago.edu/~grout/encyclopaedia_romana/scroll/scrollcodex.html
http://www.sbl-site.org/publications/article.aspx?ArticleId=248
http://members.tripod.com/~papyri/vellum/vellum.html
Codex (codices):
The codex is a book in modern format. It comprises separate sheets of writing material that are stitched together within a cover. The term is most commonly used for hand-written books (manuscripts).
There are several theories as to why the codex took over from the scroll. One is that the wooden tablet (a shallow recess was carved into its surface and filled with coloured wax) or tabula cevata, which was often fastened into leaves and used by the Greeks and Romans for everyday correspondence, students’ lessons and the like, led to the development of the codex form. In fact, it was its resemblance to a block of wood that the tablet came to be called a codex, which means block of wood in Latin. Another is that the development came from folding scrolls into an accordion format which was easier to store and handle.
It is thought that despite the physical benefits of the codex over the scroll it was when the Christian church adopted the codex form to differentiate its writings from Judaic writings, which could only be copied in the format of the scroll, and also from pagan literature, which was also associated with the roll form, that it became the predominant book form. Other draw cards for the Christian church were that longer religious texts could be contained within a single volume and be referred to more easily, and (possibly) that the codex served to indicate to Christian readers that a particular copy had a sound origin before publishers' imprints were used.
Other advantages of the codex include:
- its ability to be opened flat at any page making reading easier;
- pages could be written of recto and verso (right and left hand pages respectively);
- it was more compact and portable (replacing the wooden table ‘notebook’) and could be protected by a leather or wooden cover;
- text could be accessed at any point without first having to scroll through preceding text;
- the restrictions of size brought about by the papyrus rolls’ manufacturing process were removed;
- and the ability of the codex to accept a wide variety of mediums and techniques
By the fourth century AD the codex replaced the scroll as the predominant form of book.

References:
http://www.wordwebonline.com/search.pl?w=codex
http://penelope.uchicago.edu/~grout/encyclopaedia_romana/scroll/scrollcodex.html
http://www.hss.ed.ac.uk/chb/chbn2002_4.htm
http://members.tripod.com/~papyri/vellum/vellum.html