Pliny is one of the best-known prose Latin authors of the 1st century. We have ten volumes of personal letters that he published. Is it that you're hunting around for references to "Pliny" and finding a mix of material on him and his uncle? In case of confusion, the one you're interested in is often referred to as "Pliny the Younger"; his full name in Latin is Gaius Plinius Caecilius Secundus (his uncle, Pliny the Elder, was Gaius Plinius Secundus). He's got a short-ish but adequate Wikipedia article here, if you want general info.

If it's solely his governorship of Bithynia that you're interested in, then yes, that is a relatively obscure topic. I'd suggest the first couple of chapters of Jesper Madsen's book Eager to be Roman: Greek Response to Roman Rule in Pontus and Bithynia (London, 2009). But if you're interested in him more generally, there's a ton of books out there, mostly about his letters. I'd especially recommend Gibson and Morello, Reading the Letters of Pliny the Younger: an Introduction (Cambridge, 2012); Winsbury's new book Pliny the Younger: A Life in Roman Letters (London, 2014), which I have not read (yet), is reportedly more biography than literary criticism, so that might be right up your alley.