[Tex2002ans]

Originally Posted by 42piratas

I'm creating a picture book/epub with Sigil. There are a few images that are placed across two facing pages. How can I achieve that?

What you want is called a Fixed Layout (FXL) ebook.

These are extremely hard to produce (and not well supported).

They have to also be custom-made per device per store.

(FXL ebooks for Amazon isn't compatible with Kobo isn't compatible with Apple iBooks.)

If you want more information on advantages/disadvantages, I highly recommend checking out the fantastic article at:

• Booknook.biz: "Kid's Books"

Creating these types of books is typically very hard for a self-published person to try to do on their own.

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Note: Booknook is one of the very few companies officially approved by Amazon.

Hitch is an extremely helpful user here—that's her conversion company.

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Originally Posted by 42piratas

Should I cut the image in the middle and add each to a different HTML file? And if so, what are the CSS-related best practices to keep them together/well-aligned?

You want to hand this type of children's book over to a professional.

If you really want to do it on your own, then you can read all about "two-page spreads" in the actual specs:

• Amazon's "Kindle Publishing Guidelines" (PDF)
• Apple's "Book Assets Guide"
• Kobo's "Kobo EPUB Guidelines"
• EPUB3's "Fixed Layout Documents"

In EPUB3, you are looking for:

• rendition:spread
• page-spread-*

but like I said, this will most likely bring pain and misery. These types of "multi-page spreads" + FXL aren't well supported in the broader ebook ecosystem.

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Side Note: If you want even more information on FXL books, I wrote a few in-depth responses earlier this year:

• /r/selfpublish: "PDF or Quark Layout to ePub?"
• /r/selfpublish: "Learning how to convert my picture book for Kobo and Kindle (indd, Mobi, ePub and Fixed Format advice WELCOMED!)"

95% of the time, FXL is the completely wrong tool for the job too. (People actually want a normal, reflowable EPUB.)

In the very rare 5% of the time, which it looks like yours is, you may want an FXL ebook.

But these types of books are:

• Very expensive to produce.
• Get low sales.
• Are a pain to read.
  
  • Constantly pinch/zooming, can't change fonts, can't read on e-ink or small phones, etc.
• Very likely to break (and need updating) in the future.
  
  • See the fantastic ebookcraft 2019 talk, "Building Ebooks That Last", where an editor from Houghton Mifflin explained the pain of FXL books + warned strongly against them.

(Personally, I don't touch FXL ebooks with a ten-foot pole.)

And there's no way to JUST limit sales to "tablets" or "PCs" or "big devices", so you'll get a lot of angry customers rating/reviewing poorly too...

Usually it's best to keep these types of picture books as Print-only.

Originally Posted by jhowell

Amazon supports something similar to allow double page spreads in comics. (Creating Fixed-Layout Books with Image Pop-Ups or Virtual Panels)

Yep. In the Amazon Kindle Publishing Guidelines (2019.2), you'll want to look at chapters:

• 11 Creating Fixed-Layout Books with Text Pop-Ups
  
  • 11.6.1 Using Side-by-Side Images When Orientation-Lock Is Set to Landscape
    
• 13 Creating Fixed-Layout Books Without Pop-Ups

which describe+show examples.