I assume you don't write the HTML directly, but use something like MarkDown or reST.
But even if you do, you should look at Pandoc .
The program can read HTML and generate EPUB 2 or EPUB 3 (among others).
ebooks.stackexchange.com/users/60/Anthon
Since you mention you post to your blog each Sunday, if you have or can provide an RSS feed you may find the following online free service useful http://newstoebook.com/
I've been using it to create ebooks of one of my project blogs.
The resulting ebook (I create .mobi books for Kindles) have been readable.
I expect there will be limitations so YMMV for your blog posts.
ebooks.stackexchange.com/users/134/JulianHarty
You can use Papyrus for creating ebooks from blog posts or any webpage.
If you already have a blog, you can use this link to convert your blog to book )
Your book will be generated in EPUB, Mobi(Kindle) and PDF formats.
Disclosure: I am the creator of this site.
ebooks.stackexchange.com/users/247/gt5050
Calibre can convert XHTML 1.1 + CSS 2.1 to epub.
It's only guaranteed to output valid epub if the input is valid.
It's free and open-source.
ebooks.stackexchange.com/users/276/Ben Crowell
If your files really are genuinely valid XHTML, you could even write an XSLT2 script to do the job yourself.
That way you can cater for any idiosyncracies in your XHTML which other systems may not be designed to handle.
ebooks.stackexchange.com/users/339/Peter Flynn
I have a number of short HTML files (actually they are XHTML) with small problems and answers, which I post on my blog every Sunday, and I'd like to merge some of them in an ebook.I already did it once, just by stripping the headers and footers and merging them together; then I create the epub skeleton with Calibre and tweaked it with Sigil. But since there are a lot of internal links, it is a time-consuming process.  Is there a simpler way?
How to build an epub starting from a bunch of HTML files?
ebooks.stackexchange.com
<epub><creation><calibre>
ebooks.stackexchange.com/questions/294
ebooks.stackexchange.com/users/106/mau
You can use Papyrus to create ebooks or Calibre. There are software programmes available that could perform this task for you, including Papyrus or Calibre. However, if your files are in XHTML format, you could use an XSLT2 script to automatically create the epub.
There are software programmes available that can create an epub from HTML, including Papyrus and Calibre. If your pages are in XHTML format, you could use XSLT2 script to create your epub automatically.