for books, i would suggest anything that has large lists, such as axelrods atlas. it doesnt really have much information in it, but its a great place to start. i often thumb through it, see a fish that catches my eye, and then just look up every bit of info i can about it online. there is a lot of misinformation online, but if you use a little common sense, its easy to tell when someone is being dogmatic and claiming "facts" from a very limited pool of experience.
a good example is elassoma gilberti, gulf coast pygmy sunfish. there are references out there that say they NEED soft acidic water, with ph sometimes as low as 4. the fact that i have mine breeding happily in a ph of 8.7 in extremely hard water goes to show that the "facts" were prematurely determined by some literate individuals with access to a computer. it seems as if they had made the claim based on a single collection report from an isolated swampy location. i collected mine in hard alkaline water.
anything new is going to be pretty much the same. people will make claims, write books, and draw conclusions without first exploring other possibilities. the best thing is to look up the fish, look up the experience of others, and if you cannot find the experience of others, look up info about their habitats or those of similar fish.
for plants i usually jut google things from the list on wikipedia, or pull out the reference papers that i have accumulated ever the last several years.