Encyclopedias and dictionaries are useful publications to get a first introduction to a specific topic. You will find explanations and definitions for specific terms as well as references and suggestions for further reading.
Check out Britannica online which includes the complete encyclopedia, as well as Merriam-Webster's Collegiate Dictionary and the Britannica Book of the Year.
Below, you will find a few suggestions within some of the fields of Computer Science & Informatics. To find others you can search in Primo for encyclopedia/dictionary and your field of study.