Domain Name

I use Namecheap but there are lots of other Domain Name sellers you can choose from

Hosting

I use Namecheap but there are lots of other Hosting Sellers

Site Builder / Landing Page builder

The easiest site builder is WordPress (which is a blogging platform but is also classed as a CMS (Content Management System)
You can use WordPress to make a single page or 1,000 pages on your site.
A very popular Landing Page builder is Wix, they have a free builder with lots of templates

I very rarely build a site from scratch, I use templates and then modify them to suit my needs.

Selling the book

If you are creating a digital book, then you can sell it direct from your landing page:

Payment Processor

You will need to set up a payment processor like Paypal (the buyer just needs either a Paypal account or a credit card *doesn’t have to have a Paypal account if they have a credit card but can still purchase using the Paypal payment processor) You would be better to set up a Business Paypal Account (it’s free to do and can either be a new account or upgrade your personal Paypal.
Stripe / Payoneer  are 2 of the other popular payment processors

You will need a secure way of hosting your digital book in the cloud so it’s only accessible after a payment is made.
If you get hosting for your landing page, you will probably be able to set up a secure folder to put your downloadable book in but if others get the link to the folder, they can access it as well. In that case, you might need to set up a log in section to access it.

eBook sites – if you create it as an eBook this could be listed on the eBook specific sites and I think they would host it and take payment and provide secure downloads. Ideas of where to sell eBooks.

Amazon – they have a digital section where you can upload and list it on amazon but they do take a hefty commission – they also offer the option of turning it into a printed book for people to purchase and have delivered.

eBay – you can create your own shop but I don’t know much about how you would host and sell it through them.

As for just having a landing page, you’re better just having a look at some of the below for templates – this would be the easier option.
A list of templates and details.
Free WordPress Landing Page Templates

Or get a cheap domain (if you’re not bothered about getting a great listing in google) like a .xyz about $1 (0.73p)for 12 months and then about $12 per year after that. Like this site (2link.xyz – the webpage you are on now) I use this site for info pages like this one or for redirects like: Digital You Marketing Digital Properties and Examples