Hello: Total bicycle newbie here, not sure I'm in the right place

[Coventina]

My backstory:

The Christmas I was 6 years old, my parents bought me a ladies' 3 speed bike.
For the time, and considering their poverty, a pretty nice bike (I still have it).

My dad proceeded to try and teach me to ride.
About two minutes into this process, bicycles and I became mortal enemies.
(Have you seen those Calvin & Hobbes cartoons? That was how it went).

I was soooo far off the ground, it was terrifying, and I fell constantly.
And, this was the 1970s, before safety gear was even imagined.

Needless to say, my dad gave up in frustration, and the bike went into storage.

Time went on, and eventually, my inability to ride a bike became an embarrassment. I was the only kid in my peer group that couldn't.
Of course, other kids learned on kids' bikes.

Finally, one day when I was visiting my cousins, I grabbed my cousin's kid bike and snuck away to teach myself or die trying.
I was not quite 9 years old.
I did it, and was able to transfer (shakily) the skill to my own bike, which was still way too big for me.

As I got older, I became proficient enough that the bike was my primary transportation to and from school all the way through high school. But I still hated it.
I never rode confidently, frequently crashed (still no safety equipment commonly used), and was screamed at, had stuff thrown at me, and once had a guy try to abduct me.

Once I graduated high school, the bike went back into storage and I started riding the bus until I purchased my first car.

Fast forward to now - ish.

I have bone spurs on both heels, which makes walking, jogging, etc. just as painful as you might imagine.
My physical therapist suggested bicycling as a way to exercise without hurting my feet.

I was willing to consider it because a) I'm desperate and b) I do live in a very bicycle friendly community.

I mentioned it to my husband and WHAMMO!

On St. Valentine's Day, a new bicycle appeared!
It is an Electra Cruiser, just about as different from my three speed as possible.
Obviously, no gears and coaster brakes instead of handlebar ones.

It came completely stripped, no frills at all.

I have since purchased a helmet and gloves, both of which I am quite happy with.
I bought a headlight and a tail-light, also, a combination lock.

I've been riding it virtually every day for at least 30 minutes, although I plan to increase that, but I'm not sure how.

So here's what I want to know, if this cycling community is willing to help me out here:

1. Is there a good book on basic cycling, for "Dummies" or "Complete Idiots" or one with a less silly title?
2. Is there a good book on cycling fitness? I want to get the most out of riding for health. (Keep in mind I'm starting from near-couch-potato status. I won't be doing the Tour de France for awhile).

I am planning on buying for the following in this order (unless I should re-prioritize?)

1. Bell
2. Fender set (after a rainstorm, I got a lot of splash-back from my tires)
3. Basket for handlebars
4. Rear rack
5. Rear-view mirror
6. Water-bottle holder
7. Tool kit? (but at this point I know nothing about bike repair)
8. ?????

Anything else?

Any other advice for a cycling newbie?