Having never read Ann Rice's novel I cannot comment on the accuracy of the film. What I will say is that, on its own strengths, this film is essential viewing. Those seeking thrills and frights should turn away now, those interested in depth and character development should buy this instantly. Tom Cruise turns in a great performance as the lonely, malicious vampire Lestat, with Brad Pitt as his brooding, conscience-stricken protege. Despite the fact that the leads are all vampires and drink blood, at times quite graphically, you cannot help but feel sympathy for them as prisoners of eternal darkness. This is partly because of the phenomenal acting on offer and partly because of the screenplay. Some very intense issues are dealt with in the course of the film, Louis struggles with his morality over killing people for a large chunk of the film until eventually he resigns himself to his fate, biting a young girl (Kirsten Dunst). The scope of the film expands from just Lestat and Louis in America to a whole secret society in Paris, along the way revealing some of the vampire laws and customs. The plot also spans a huge time period, ending in the modern day with Louis telling his tale to a journalist (Christian Slater). After watching this film I remember thinking to myself "yeah... if vampires existed I could see them being exactly like that," Rice's vampires are still human, they just become resigned to the fact that they have to drink blood to survive.
My advice is if you like the sound of my review go out and buy the film. If you are not sure definitely rent it, you never know, it might surprise you.