If you really want to read up then: F N Howes Plants and Beekeeping & The Bee Friendly Garden by Ted Hooper.
There is little you can do to significantly affect the main honey flow, although single bloom flowers/cottage favourites help eg calendula, cornflower, mallow, sedum, delphinium........and 'weeds' such as dandelion, white clover and rosebay willowherb. And also anything from the lamiacae family.
The main honey flow will most likely come from lime trees, sycamore, brambles, w. clover and rosebay willowherb to name a few.
One thing you can do to really help a colony is provide early sources of nectar and pollen. These are really vital for a colony having just come through/coming through winter.....snowdrops (again single), winter aconite, mahonia, crocus and willow and hazel are brilliant for that and every beekeeper should plant such early sources of forage.