In Roger, use microb* (with the *) to search on multiple microbiology-related terms: microbial, microbes, microbiological, etc.
Warning: use this term (microb*), or any broad truncated term (i.e. using the "*" wildcard) WITH your specific subject terms, because used alone in a search they will retrieve very general and large results.
For example: marine microb*, marine microb* biodivers*, sponge microb*, probiotic microb*, etc.
If you don't have an author or title, start with the keyword search.
Searching marine microbiology is the same as marine and microbiology, and will retrieve only records with both terms.
Searching microbial or microbes will retrieve results with at least one term, giving you a very larger set of results.
Recommended search if using OR: (microbial or microbes) and marine
If you see >> Go to electronic version in the record, most of these will be links to the online book, an e-book.