Interlingua is much more Romantic than Esperanto, which was strongly influenced by Germanic and Slavic languages. And it's more Romantic than, but still quite similar to, Latino Sine Flexione, which sticks pretty much to a Latin vocabulary with simplified grammar. Interlingua has much in common with Occidental; however, Occidental vocabulary and grammar appear to have been heavily influenced by English. And then there's also Latino Moderne, about which I haven't found a whole lot of information.
In addition to the usual IAL uses, Interlingua is being used by Numinists and also by the citizens of Nova Roma. And in early 2001, the europa.* newsgroups were born; initial working languages appear to be French, English, and Interlingua. (There is some suspicion that the hierarchy was created by Interlinguists as a means of promoting Interlingua as the IAL of the European Union. If so... nicely done!)
Books may be purchased from some of the websites listed above. The following books were also found at Amazon; some others were listed, but out of stock when I checked.
Un policiero ha stoppate le automobile de Werner Heisenberg.
"Sape tu," le policiero ha dicite, "a que velocitate tu era vadente?"
"Non," Heisenberg ha respondite, "ma io sape ubi io es!"
Un studente de physica ha vidite Albert Einstein in un traino.
"Excusa me, Professor," le studente ha demandate, "sape tu si New York stoppa a iste traino?"