Why interesting? Because it brings good luck?
No, since there are 12 zodiac signs, all issues on this theme, are small series.
Mainly with the usual designs, but sometimes with very artistic paintings, designs, colours...
First in my list of zodiac series, is a recently issued, belgian set.
And right from the start it's already a very interesting issue.
On the side, there are 12 zodiac signs, that can be taken out of the sheet and put on the circle on the stamp.
Smart move of the belgian postal services of course. Since collectors who want to have all 12 signs in used condition, need to buy already 2 sheets - or 3 sheets if you want all stamps in mint condition too.
You can also add a 13th stamp - the neutral one without sticker, just the 12 signs in the circle.
I do have to tell that the two signs on the right bottom of the sheet (Gemini and Cancer) are slightly more difficult to remove from the sheet then the other signs.
Being a Gemini myself (or Cancer according to some glossy magazines), i noticed that the sticker of those two signs got damaged sometimes when removed from the sheet.
So, it might be more difficult to find those signs on used stamps.
So maybe, in the future, my sign will be more valuable then other signs.
Being a rational person, of course i don't believe in this kind of nonsence. But that is typical for Gemini i've been told :-)