I'm using the Norton Anthology of English Literature and am wondering how I can supplement it with critical readings. Do you have any suggestions, especially with regard to Gothic literature?
Most editions of the Norton Anthology of English Literature contain detailed bibliographies, at the very ends of the volumes, dealing with critical writings about various authors and topics. The latest edition drops those bibliographies from the printed book and moves them to an online site -- a decision that is both good and bad.
Your best bet is to check the Library of Congress (see link below). Once you are at the main Library of Congress page, click on “Library Catalogues.” Then in the “subject” box, type the words “Gothic literature,” and you will find hundreds of relevant entries on books dealing with this topic. Once you are at that page, check under “bibliographies,” where you will find guides to research on this topic. The bibliographies by Frederick S. Frank look particularly helpful.
Don’t forget that there are plenty of useful online sources dealing with this topic. Copy and paste this link into your browser for examples: https://www.google.com/#hl=en&sclient=psy-ab&q=gothic+literature+annoted+bibliography&oq=gothic+literature+annoted+bibliography&aq=f&aqi=&aql=&gs_l=hp.3...1155l9898l0l10420l42l34l2l6l6l0l370l5690l0j30j3j1l42l0.frgbld.&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=87c6230bd8e448f1&biw=1366&bih=624
Annotated bibliographies are often especially helpful since they can give you a quick overview of articles and books of special interest as well as of the issues most often discussed and the conversations and debates they have most often provoked.
See also, of course, the excellent eNotes sources cited below. One advantage of subscribing to eNotes is that you have an enormous number of critical sources literally at your fingertips.