Joseph Hudak wrote an excellent generic description of a genus of very valuable shade tolerant perennials, "Foliage is the main asset of Hosta, and it appears in mounds at ground level in a variety of colorings from light to dark green, yellow-green to almost-yellow, and blue-green to grayish green with leaves lance-like, heart-shaped, or oval in form. Some are streaked, mottled, or margined in white to yellow as a bonus. When grown well, an Hosta creates an exceptional summertime ground cover with secondary interest from its flowering. All of the types blend well with each other and offer splendid possibilities for texture and color in shaded areas."
Beth Chatto's description of Hostas was a good deal more succinct but very persuasive, "No other plant has the same impact."
Even when Hostas comprise most of the plants in a composition they offer enough variety of leaf sizes, colors and textures to make that composition look much more varied than it actually is.
Hostas in the first photo and in adjacent beds [In no particular order]:
Hosta 'Blue Angel'
Hosta 'Krossa Regal'
Hosta 'Hadspen Blue'
Hosta 'On Stage'
Hosta 'Captain Kirk'
Hosta 'Queen Josephine'
HOSTA 'BLUE MOUSE EARS'
(a grouping of 5)
(flanking a small clump of pink Balloon Flower))
(flanked by 2 Hosta 'George Smith')