The short answer to this question is: none. No ancillary reading is necessary to enjoy Ulysses, and I tend to tell first-time readers to actually avoid all the guides and reference books: I think it’s best to just let Joyce’s prose carry you along, and enjoy the ride. You can try to figure out “what it all means” later.
However, I do recognize that this approach isn’t satisfying to everyone, and some people prefer to have some of the more difficult aspects of the text cleared up for them as they go. (This seems an appropriate thing to acknowledge in the light of Daryl’s post earlier today). So here are some of the things that you might like to take a look at, as we read.
1. In addition to a good dictionary, the one indispensible resource is Don Gifford’s Ulysses Annotated. This hefty tome will elucidate the vast majority of Joyce’s references, from literary allusions to local Dublin “street furniture.” Some people like to read with this open alongside, checking out Gifford’s commentary as they go. I did this, in fact, my second time through: it’s enlightening, but as you might imagine it really slows down the reading, and takes a lot away from the rhythm of Joyce’s writing, so I’m not crazy about it as an approach. Instead, I’d suggest marking words and passages you are curious about as you read, and then after you finish a chapter go to Gifford and look them up. But everyone reads differently, and you’ll have to find a method that works for you.
2. There are any number of guides to Ulysses, which provide plot summary and explain various allusions and parallels. There are two that are particularly worth mentioning. One was written by Joyce’s friend Stuart Gilbert, with Joyce’s guidance, and so it has the authorial imprimatur: it’s sort of the “official” guide to Ulysses. It is an excellent book. It’s rather heavy on the summary and quotation of the novel, but when you consider that it was published while Ulysses was still banned in most of the English-speaking world, that makes a lot of sense. Gilbert spends a lot of time on the Homeric parallels, cementing that mode of reading for a generation of Joyceans. His introduction to the book is fascinating (and almost as dense as Ulysses itself, at times), so I’d suggest looking at that at some point (preferably after you’ve finished your first reading of the novel), even if you don’t want read his summary/analysis of each individual chapter.
More recent than Gilbert, and rather more popular among contemporary readers, is Harry Blamires’ The Bloomsday Book. This is a lot less inflated than Gilbert’s book, and provides a sort of walk-through of the text, pointing out various connections that might escape the casual reader. It’s very helpful, but I often find myself questioning his conclusions. (I believe I’ve spotted a few outright errors, in fact.) But really, I think my problem is that I just find his reading a little too cut-and-dried, whereas I find Ulysses is more ambiguous.
Then there is a more recent guide, which I’ve heard was actually a best-seller in Ireland (though I have not confirmed this to be true): Declan Kiberd’s Ulysses and Us: The Art of Everyday Living. As the title suggests, this is less a guide to the plot of the book or exegesis of its literary depths than a discussion of what the book has to tell us about being human. In that regard, it’s maybe a little touchy-feely for some, but it’s really quite good, and it’s interesting to see how Ulysses is regarded “today.” (Well, last year, anyway.)
3. Moving up the scale from “notes” to “guides” to “studies,” there are any number of great introductions to Ulysses that take a more whole-cloth approach, rather than walking the reader from chapter to chapter. One I particularly like is by Hugh Kenner, probably the greatest modernist scholar of his generation, and just a really good stylist in his own right. His book on Ulysses is brief, but full of interesting observations. There are others, but this is my favorite.
4. Then there’s the literature that Joyce was drawing on for background. I don’t think reading the Odyssey is very important for understanding Ulysses: a grasp of its basic plot (a hero trying to get home, a son trying to reunite with his father) and major characters and mythological monsters (Cyclops, Sirens, etc.) is sufficient, and can be gained from reading a children’s “stories from the Odyssey” (which is, I believe, essentially what Joyce was drawing on). But if you have the time, of course, there’s no harm in reading the Great Poem of the Western Tradition (I like the Fagles translation).
The other big canonical text referred to throughout Ulysses is Hamlet. I’d imagine everyone reading this has read Hamlet at some point, but if you have a free couple hours, it’s worth revisiting it: there’s a whole chapter (the ninth) that centers on it, so it’s good to have it fresh in your mind. But not necessary, by any means. (As a matter of fact, the discussion of Hamlet in the book strays pretty far from the play itself, looking more towards Shakespeare’s life for material. But you’ll see.)
The most important precursor to Ulysses is Joyce’s previous novel, A Portrait of the Artist as a Young Man. This you probably should read before you start. Ulysses picks up the story of Stephen Dedalus where Portrait left off, and a number of other characters carry over as well. Again, you’ll totally be able to get into Ulysses without it, but it provides useful context. There are also a number of characters from Dubliners, Joyce’s collection of short stories, that crop up, but it’s not necessary to have read that one first either.
5. And of course, like all his books, Joyce drew much of Ulysses from his own life, so Richard Ellmann’s magisterial biography provides a lot of useful background.
Of course, there’s also a lot of stuff online (for example, the annotations at Ulysses “Seen”): my next post will explore Ulysses on the web. And I’d like to invite comments on secondary sources from you, as well: I’m sure there’s a lot of stuff I didn’t mention, and probably people have their own ideas on how to best approach the book: please share.
Ultimately I’d like to reiterate, even though I’ve listed a semester’s-worth of reading here, absolutely none of it is necessary, and I strongly encourage first-time readers to just jump into the book without all this excess baggage holding you down. The book more than stands on its own.