It's only a problem if it is keeping you from some goal. Example: If you're doing a research report on a certain president and you find yourself reading up on a dozen other interesting presidents, well that's a problem because it keeps you from finishing your report. On the other hand, if you are interested in genetic algorithms and you wind up reading about real genetics, epigentics and then Dawkin's book "The Selfish Gene", I don't see how that is bad.