First it is important to note that case reporters as we understand them are relatively new in the field of law. In England in the earliest periods any document dealing with a case was a sealed record. Additionally, there were no official reporters. As such, reporters containing cases from those times draw their materials from other sources. In the earliest periods the only materials available were the notes of law students/apprentices who were observing the trials and taking notes. Later these materials were supplemented or replaced with the notes of judges and counsel. This continued until the first official reporter in England was adopted in 1865. The important note here being that as you read cases from various centuries the style of case reporting will vary widely.
This is a non-exhaustive list of the Selden Society resources available at Oklahoma City University School of Law (the list is only a "highlights" list, many more are available). The Selden Society books are grouped together in the North Wing on the 3rd floor of the Law Library. Please feel free to visually peruse the collection at that location or search the Law Library Catalog.
The "select cases" type volumes are those volumes that are titled similarly to "Select Cases in the Court of King's Bench Under Edward I." These types of volumes are exactly what they sound like. They are selected cases from the King's Bench during the time of Edward I, or whatever time period the relevant volume covers. Additionally, there are also "select cases" volumes that do not restrict themselves to a particular king's reign, but cover a much broader time period and deal with a particular subject in the law, e.g., trespass. These volumes contain various indexes. These include an Index to Statutes Cited, an Index of Names and Places, and - most importantly - an Index of Matters (also called an "Index Rerum"). The Index of Matters/Rerum is a topical index allowing you to locate cases dealing with a particular topic, e.g., Novel Disseisin.
The "Year Books Series" are organized by year, each volume usually representing only one or two years during the reign of a particular king. These books are unique in that they include a "syllabus" (editor's explanation of the case - similar to Westlaw) before each case. These volumes also contain various indexes and tables. Commonly included are a Table of Statutes, Table of the Forms of Action, Table of Cases, Index of Persons and Places, and an Index of Matters.
Other types of volumes in the Selden Society Publications are those dealing with particular types of courts, pleas, and rolls. These volumes may deal with cases heard by a particular court, certain types of cases, or those cases recorded on a particular type of Roll (e.g., Coroner's Rolls, Curia Regis Rolls, etc...).