Didn't really want to make a whole thread for this, but

>>1111557
adjustable dowels

>>1111557
maybe a half-lap joint? depends how experienced you are at wood-work

File: making_interlocking_shelves_4.jpg (10KB, 400x331px) Image search: [Google]

10KB, 400x331px

>>1111557
easy

File: throughhalfblindandblind.jpg (17KB, 900x269px) Image search: [Google]

17KB, 900x269px

>>1111557
Vertical pieces should be solid, horizontal pieces attached by dado/groove joint. Make the vertical pieces thicker if needed.

>>1111576
Ikea shit tier. Very wobbly. No do.

>>1111557
make shure not to accidentaly build a shelve you don't want

>>1111665
This, half blind with additional through going dowels should work.

>>1111665
1111576 is not wobly if it is combined with a solid outer case work that uses joints like the ons you illustrated or dowels or pocket screws to hold the dividend shelfs solidly to the outerr structure.
To answer op. It depends on what your putting on them.

If they are going to hold a lot of weight and your comfortable with joint work , the use sliding dove tails, or rabits like suggested .

If you want adjustable shelfs use shelf dowels. If you know a fixed size and are not comfortable with joint work use a kreg jig and pocket screws or dowels and glue.

If it is going to be mounted to a wall then the half cuts show above would work too.