Recommendations On Book To Read.

Hi Barbara, I'll reply to this post first.

To be honest, I wouldn't recommend any books as so many of them are either out of date or don't give proper information. I'm also replying to your other threads/posts so I'll give you more information in this one https://forums.thinkfish.co.uk/say-a-big-hi!/newbie-hello/msg35102/?topicseen#new

Tropical means fish that need to be kept at around 25 deg C and can be fresh water or marine water. And there are a few that like slightly salty water called brackish water. The three can't be mixed.
Of the three, freshwater is easiest because you use plain tap water, you haven't got to add salts to make it brackish or marine. I would start with freshwater fish, then once you have experience of that you can decide if you want to move on to marine (which are more expensive and less forgiving if things go wrong).