Where you live will greatly impact what you can or should start now.
Also, are you growing indoors or outdoors?

I live in the San Francisco east bay and have an unheated greenhouse which is where my tomatoes are right now.

There are lots of books, but most are crop specific (at least for going into detail). So your probably better off deciding on what you want to grow first. You can grow just about any crop hydroponically. However if you plan to grow outside or in a greenhouse that's not climate controlled, you'll need to deal with your local climate. The best way to find out what grows best in your area during your seasons, is by going to your local nurseries and asking them what grows best during that time of the year.

Here are a few good hydroponic book titles:

(1) Hydroponic Food Production-Sixth Edition (by Howard Resh)
(2) Hydroponic Home Food Gardens (by Howard Resh)
(3) Hydroponic Tomatoes (by Howard Resh)
(4) Hydroponic Questions & Answers (by Howard Resh)
(5) Hobby Hydroponics (by Howard Resh)
(6) Hydroponic Strawberry Production (by Dr Lynette Morgan)
(7) Hydroponic Capsicum Production (by Dr Lynette Morgan)
(8) Hydroponic Lettuce Production (by Dr Lynette Morgan)
(9) Fresh Culinary Herb Production: A Technical Guide to the Hydroponic and Organic Production of Commercial Fresh Gourmet Herb Crops (by Dr Lynette Morgan)

You can print this out, It's from the University of Arizona's Controlled Environment Agriculture Center. Pat told me she was going to revise it for the fall classes (she wrote it, and teaches the classes), but wont be many changes. Scroll down to the "Curriculum" section, all the chapters are in PDF and you can print out specific chapters. Or print them all out and put them in a binder like I did.

PLS 217 Introduction to Hydroponics and CEA

Great information-thank you.

does anyone have any of those book.My e mail is srdjan.boskovic70@gmail.com
if anybody have books I have a few question.Thanks

Are you using a "heat sink" in your greenhouse?

How about peppers. Now would be a great time to get a head start as you should have very sturdy and woody stems by July. August and September for heavy production with a harvest in October would be feasible....

Here is a link that might be useful: My Indoor Growing Adventure