Your search for books might start in one of two places...
Especially if you are searching for books, you can use a Subject Search. This is very useful in literary research because it allows you to find all the books on an author, and only the books on that author.
For more information on subject searching, please see the general guide to literature research:
Searching for authors as subject is less helpful here than usual.
However, there are many subject headings concerned with gender, transgender issues, and sexuality which you may find helpful. Some of these consider transgender issues specifically. Other headings don't explicitly reference these issues but may still provide a useful analysis of gender in literature or history.
Note that browsing the list of subject headings is very useful, as many of these headings are further broken down. In particular, many of these headings include a History subheading that you can use to find historically specific analyses.
Also note: not all these subject headings are the terms that trans folks or their allies may prefer to use. This is partially because subject headings change slowly, so they may become outdated. However, you need to use the headings that are used in the system to find the works categorized under them.
The library has both print and electronic materials on these subjects.
Browsing the print collection can be especially useful when you're trying to get a good idea of where the focus of the conversation is. Furthermore, since your interests may intersect with those of the books you're using in some ways but not in others, it's useful to have the entire book in front of you to flip through.
Here are some call ranges that have useful materials:
As for the more literature-oriented books in the library holdings, you can find some of them in the PS 153 ranges, which focus on the literature of specific groups, including:
Of course, gender, sexuality and transgender issues can show up anywhere in literature -- be sure to check the call ranges dealing with specific authors, and remember to browse near any good books you find.