In Bleak House by Charles Dickens, the viewpoint frequently changes from Esther Summerson, or first-person, to third person. What is this style known as? Also, why did Dickens place such a important emphasis on Esther Summerson as to relate through her, since he also used an omniscient third person POV?
It depends on whom you ask. Some will tell you that the widest POV is the controlling factor, because narrowing it down is only an exception. In that case, Bleak House is omniscient (or third-person) POV.
Some will tell you it's alternating or multiple POV. There isn't an official name for this classification, since there are so many possible variations.
Some will tell you it's omniscient/first-person POV, because those are the two POVs used, end of discussion.
A better question might be, why did Dickens choose this format? Is Esther so much more important than any other character? Did he start out one way and change his mind? Was he going for contrast, character, or narrative logic?