Book Levels

Book Level	Description
Ungraded	An ungraded text has no inherent difficulty level, and does not require comprehension to any special degree.
1 - Introductory	A level 1 text is aimed primarily at those in their first year of a university degree. Such texts are introductory, but not neccessarily simple - they cover a particular topic from the start (usually), but are unlikely to be suitable for those younger than university age.
2 - Intermediate	A level 2 text is aimed primarily at those in their second year of a university degree. Such texts are not introductory - they assume some level of knowledge (this assumed knowledge will be detailed in the book table of contents).
3 - Advanced	A level 3 text is aimed primarily at those in their third year or last year of a university degree. Such texts assume a large amount of knowledge, and at least two years of experience with the topic at hand.

Book Versions

Book Version	Description
Alpha	An Alpha Draft has never seen the light of day before its publication on this website except within a very select group of people. Such texts require considerable editting and revision before they are production ready, and so your feedback is important on these. Such texts can and will change frequently - there is no guarantee the book you read one day will be the same as the one you read the next day.
Beta	A Beta Draft has been used for teaching for at least one year, and so has had substantial revision from its first Alpha Draft. These revisions may include extra chapters, removed chapters, reworked text and examples. The book is still considerably rough and needs further revision, and so feedback is important. Changes to these can be regular, but unlikely to be made on more than a weekly basis at most.
Delta	A Delta Draft has been used for teaching for at least two years, and is only one version away from being judged as production ready. Feedback on these books should concentrate on errors rather than suggestions for content. Changes to these are likely to be made on a monthly basis at most.
Production Edition x.x	A production edition is a finished version of the book, and additions and improvements will be based largely on long term feedback. Such books can be considered stable - you are unlikely to see changes on a regular basis - it's far more likely that a new edition will simply be published.