Plants have leaves in many different shapes - the thicker the book you refer to, the more leaf shapes they seem to find, but here are some of the basic ones.

Sometimes the Latin name will indicate the leaf shape, so I've put the Latin specific epithet in as well. This will help you identify a plant (if it has that epithet in its name, that's what the leaf will look like), and, on the other hand, if it has that shape leaf, it's possible its Latin name will contain that descriptive adjective.

Sword-shaped (ensiformis) Long, thin, pointed	Lance-shaped (lanceolata) Long, wider in the middle	Ovate (ovata) Oval, with a tapering point	Elliptic (elliptica) Oval, with a short point	Round (rotundifolia) Circular	Cordate (cordata) Heart-shaped
Oblanceolate (oblanceolata) Top wider than bottom	Spathulate (spathulata) Spoon- shaped	Rhomboid (rhomboidalis) Diamond- shaped	Lobed (lobata) With several points	Spear-shaped (hastata) Pointed, with barbs	Pinnatisect (pinnatifida) Cut, but not to the midrib
Pinnate (pinnata) 2 rows of leaflets	Bipinnate (bipinnata) Each leaflet also pinnate	Tripinnate (tripinnata) Each leaflet divided into 3	Trifoliate (trifoliata) Divided into 3 leaflets	Palmate (palmata) Divided into many lobes	Digitate (digitata) Divided into 5 lobes
Opposite (oppositifolia) Leaves opposite one another	Alternate (alternifolia) Arranged alternately	Perfoliate (perfoliata) Stem through the leaves	Peltate (peltata) Rounded, stem underneath	Whorled In circles round the stem	Rosette Leaves in close rings

Often a single plant will have leaves of several different shapes, so any description has to be taken as an indication of what you can expect to find on a particular plant, rather than a description of what they will look like. I have one book that uses phrases like 'ovate-lanceolate to obovately-cordate', but I prefer to keep it simple, and accept that most of the time the leaves will be fairly variable but roughly correspond to a basic shape.