As written, Knowledge skills cannot be retried. Characters without ranks in a knowledge skill cannot attempt a check with a DC over 10. (DC 10 representing "common knowledge")
Libraries, books & Knowledge skills
Specific books can aid in using the Knowledge skill. These types of books are detailed below.
*General Reference book: can be used to Take 10 on a Knowledge check relating to a single knowledge skill, even after a failed check. Provide no bonus,
requires 1d10 minutes to use. Allows untrained characters to attempt checks with a DC over 10. Cost 100 gp.
*Special Interest book: grants a +2 competence bonus to a Knowledge check regarding a single knowledge skill, but doesn't provide retries or Take 10. Requires 2d10 minutes to use. Allows untrained characters to attempt checks with a DC over 10. Cost 150 gp. (There are also magically enchanted books that may provide a higher bonus)
*Practical Inquiry selection: multiple different books, can be used to "Take 15", even after a failed check. Allows untrained characters to attempt checks with a DC over 10. Provides no other bonuses, requires 1d10x10 minutes to use. Cost 500 gp.
*Research selection: many, many books. Can be used to Take 20, even after a failed check. Allows untrained characters to attempt checks with a DC over 10. Provides no other bonuses, and requires a minimum of 4d4 hours to use. Cost 2500 gp.
Libraries contain many, many books. Larger libraries have more books, making special interest books easier to find, but the difficulty in finding specific tomes become harder as the total number of books increase. When designing specific libraries, the DM may identify what skills are supported at what level, or the table below may be used to represent generic library collections if the DM does not wish to detail the contents of a given library.
Library Size Search DC
General...Special Interest1...Practical Inquiry2...Research3
Personal......10............N/A..................N/A....................N/A
Small...........11............23....................N/A....................N/A
Medium.......12.............21....................N/A...................N/A
Large..........13............19....................25......................N/A
Expansive...14............17....................25.......................25
Legendary..15............15....................25.......................25
(someday I'll learn how to format tables in HTML...)
Searching for books requires one hour.
1Characters may not retry a search for Special interest books. Either the library has the book, or it does not.
2Gathering the books required for a Practical Inquiry requires three successful checks. Retries are allowed.
3Gathering the books required for Research requires five successful checks. Retries are allowed.
A Personal Library consists of ten or more General Reference books, with a minimum value of 1,000 gp. Small
and Medium libraries are defined as having one or more Special interest books, in addition to the General reference books, and may range in value between 1,150
gp and 2,500 gp in total value. Large libraries feature the same range of books as the prior categories, but also have enough books for multiple practical
inquiries; the total value of a Large collection is a minimum of 3,000 gp and as much as 8,000 gp. Expansive libraries have a minimum value of 8,000 gp, and
may have as much as 22,500 gp depending on the number of subjects supported. Legendary libraries have a minimum
collection worth 25,000 gp, and may be much more. For any given library size, some may deal in both knowledge and practical skills, and may have a higher valued collection. These values are solely for Knowledge-based libraries; those that also feature support on
survival, crafts, or professions would include even more books. Libraries for researching magical studies such as Spellcraft would not necessarily follow these
standards.
These guidelines cover only general knowledge, and the ways in which reference books can assist the memory of characters. These rules are not all-inclusive;
indiviual books may contain specific pieces of knowledge, and these rules are not meant to supplant that concept.
Feedback is appreciated!


