I have an iPad Air which I like, but it is pricey.
Most devices do NOT have a monthly charge. The monthly charge is if you buy a device (such as an iPad) that has cellular capabilities (cellular costs an extra $100 on an iPad). Cellular capability means you can hook it up to your cell phone account (usually for $10/month) so that, if you take it outside your house to a place that doesn't have Wi-Fi, you can still cruise the net by means of your cell phone's data plan (assuming you have a smart phone which requires the data plan).
Assuming you have internet in your house, you can simply create a wi-fi network in your home so your device can hook up to the internet by means of your wi-fi network. I believe wi-fi is free and easy to do with most internet providers. My daughter, who has CenturyLink for internet, simply had to enter the password on her router into her iPad in order to link the iPad via wi-fi to her CenturyLink internet.
Are you sure you like reading on an electronic device? I would never consider reading a book on my iPad (or any other reader) because I just don't like it. If you have a BestBuy near you, I would recommend stopping in there several times to try out the various tablets and readers they have. Also, BestBuy floor people are well-trained and can explain many of the differences (and they are not on commission, so you don't need to feel obliged to buy).