You see, that's where many people get caught up.
Photoshop is fantastic for doing weird and wonderful things. You can manipulate images and text and colours like there is no tomorrow.
It is fantastic. But that is photoshop, it is for manipulating things like that get a great appearance.
That's where InDesign comes into play. InDesign isn't an image or photo editor. InDesign is Page Layout application. This is where you bring in all your elements from external or previous made elements.
The main difference with Photoshop is that it is primarily geared towards Raster (bitmap/pixel) images. That means that if your image is 300 dpi, then you can't increase the size of it without distorting the quality of the image. The whole program is primarily based around bitmap.
So you look at Illustrator next, you can do wonderful illustrations, they are primarily vector based. There is a plethora of things you can design in Illustrator (even redrawing human faces to extraordinary accuracy) the beauty about this is because they are vector based (mathematic equations) they can be increased to almost any size imaginable.
Where InDesign is a happy medium, this is where you bring in your wonderful Photoshop Images, along with your Illustrator items. This where you plan them up on a page. Because InDesign is a page layout program, it's not an Illustrator package and it's not a Photoshop package. It's completely different. It's to bring all your wonderful artwork that you created in different apps, whethere they are Vector or Bitmap and you can layout your page to your liking.
Along with this you get fantastic text control, facing pages, single pages, any page size, margins, columns, keep options, paragraph/character/object/table styles, base one style on another etc.
InDesign is the application that brings all your elements together and gives you the opportunity to lay them out in book or brochure or single page layouts, that is easily exported to PDF to send to a printers.
You wouldn't put a 4 page booklet together in Photoshop(you can but it's a nightmare, especially when you get to booklet/books with more than 8 pages, where you need folios, running heads, master pasges, styles etc.)
So don't dismiss InDesign, it's an immenseley powerful Page Layout application, that ticks far more boxes in terms of PAge layout than Photoshop or Illustrator put together.