To serif or not to serif?

The tiny skirmish with the delights of letterpress and typography has whetted my appetite to do more - but left me none the wiser about what font is suitable for what text. In my working life, fonts were already decided as a matter of house style, but for making individual books, the choice of font can cause all sorts of problems ... for instance, for the book of sonnets that I  rewrote as part of memorising them. Here are two possibilities - "modern" versus "ancient" -

Someone who looks at this rather incomprehensible book is owed an explanation of what's going on. The title page seems to be a good place for that - and given the sonnet's popularity "long ago", a title page that reflects the title pages of that era seems appropriate - hence the old-fashioned looking type. And yet - two of the ten poems were written in the 20th century, and my book was written in the 21st, so why not use a sans-serif font, which I understand is the modern way of doing titles ("display matter") even if text is in a serif font.

As it turns out the serif font I blindly chose from the drop-down list is Perpetua, which I now discover was designed in 1925. It's classified as a transitional type (it has high stroke contrast and bracketed serifs) so might be entirely approriate. But I'm still thinking about it....