There are almost as many definitions and different sorts of love as there are poets. Edited on the assumption that any poem which speaks of one human's desire for another is a qualifying factor, ''The New Penguin Book of Love Poetry'' is a rich and diverse anthology which ranges through time and fashion. Passion, urgency, simplicity, heartbreak and renunciation are all here in a volume that superbly represents 'man's changeless responses to the changeless changing seasons of his heart'.