Dolly Roman is neutral and useful for long texts. Dolly Italic is narrower and lighter in colour than the roman, and can be used to emphasize words within roman text. Dolly Bold is also useful in emphasizing words within roman text, but also works well as a display type. Dolly Small Caps are intended for setting whole words or strings of characters while regular roman capitals are used only for the first letter in a word.
With its relatively low contrast Dolly is perfectly legible in very small sizes. When Dolly is applied in larger, display sizes (like book covers), more crispy details will show up which are invisible in small sizes.