Aligning pages side by side with 0 space between

It's a drop-down next to the alignment icons on the top bar:

Choosing the alignment method can completely change how the selected elements align.

Well, no humble pie needed. We are all always learning and growing. I'm glad that my silly issue that I overlooked is helping you to find an easier way. All the best,

I'm going to disagree that this is "the correct way" and that I was "wrong" above... however, I do cop to misunderstanding and saying a couple of confused things at the start.

There are two basic ways to lay out a cover: on a single page, using frames and groups to manage the content for each surface and allowing easy placement and adjustment of elements that bridge any of them; and the three-page method, which is essentially the same thing but takes advantage of ID's abilty to do multi-page spreads.

With one page, all layout is "soft" and can be adjusted as necessary without any limitations I can think of.

With three pages, you start with a hard framework that offers no real advantage over three content frames and imposes an extra layer of management  — and is dependent on something of a hat trick to output correctly. Yes, exporting spreads works fine, but I would not be surprised if it has the potential for frustrating glitches and complications at the export/PDF stage. (Transparency lines, anyone?)

I lay out a fair number of covers and because many of my books are updated at intervals, the spine width does change. It takes me a minute or two to set the new page width to whatever the printer or service specifies, then (if needed) tweak the position of the front and rear cover groups, leaving the spine group centered. Elements that span two or all three faces can be adjusted with ease.

With the three-page layout... it's exactly the same, assuming you have defined width bleeds that accommodate the trim range. But unless you adjust the spine width numerically, the content is going to shift off center and need adjustment of it, or both outer pages. (Am I missing some technique that allows for change of a page width while keeping vertical content centered?)

And all of that added management is solely "to allow spine width adjustment," which for most books is a one-time task, and which — in my experience — is trivial to do with a single page layout.

I'd say the techniques are at best equivalent, but the three-page model trades one advantage for several actual and potential disadvantages. For things like a book series (reports, annual volumes, etc.) where a major task in each interation is setting a spine width, it mght have an advantage. But most "art" covers don't have three compartmented sections of content, and breaking it into pages imposes some design and manipulation limits that a single page does not.

So, at least two techniques, both of which work for the common end need. Neither is wrong, I think. But each has a better range of use.

—

Thank you! I will look into that! I'm honestly kind of new to InDesign, though I've been using Photoshop in my business for years. The tutorial I watched said not to tick facing pages, and I'm wondering why she said that. I'll have to watch it again to see if I might have missed something. Or maybe something has changed since she made that tutorial and what used to be better, now isn't. It would be great not to have to mess with alignment at all. 

I must be misunderstanding you here. Are you working with three actual document pages, or three frames on one page layout?

—

I'm placing a photoshop document across all three pages in InDesign. It just makes adjusting the spine width very simple.