I feel like adding dialect isn't something that makes the greatest difference to the story. It defiantly helps in making the the setting feel more authentic, especially if it is in a foreign country. The setting is defiantly an important part and making it feel real (if your choosing to do that with added dialect) it only expands the story. I always felt like the story line and characters are what really make a book enjoyable and immersive. I think that is why I enjoy the books you write. I've read Mariana and The Rose Garden (currently reading The Winter Sea) and both have dialect from certain periods. It really lets you feel like you traveled back to those time periods with the characters. The fact that the story is so compelling, the characters are so relate-able, and I feel completely immersed into the surroundings is why I'm just really enjoying these book so much.