Yes it’s o.k., and yes it’s expensive. I think a better plan is to only pack things that you know without a doubt will get used a lot. Everything else is (heavy) fluff—so leave it at home.

Consider buying the guidebooks used (often very cheap from Amazon) and rip out and take only the parts you’ll need. Personally, I prefer doing my research in advance, and make lists of top lodging options, highlights, and transport basics that I print out front/back, fold and take along. You can always drop in the tourist info office if you need more info or advice once arrived.

Take one general guide book — or, as Don suggests, the pages from it. If it gets to be too heavy, leave it behind at your hostel. If you really want it after you get home you can buy a used one to replace it for less than it cost to mail it home. Same is probably true for at least some of your clothes — if it’s basic, you can probably replace it for what it costs to mail it.
How long is your trip? How much time do you want to spend hunting up packaging materials, finding the post office, standing in line and dealing with the language barrier for mailing options?

If you’re going for a week or two, pack all of your old/undesirable t-shirts, underwear, socks, etc. and throw them away as you use them.

I’ll be gone for 1-2 months. Thanks for the advice (:

In that case, if you have the money, bring almost nothing. Buy your toiletries in Europe. They are souvenirs. (Still wish I had the shampoo from Budapest.) You can also budget to buy some of your clothes in Europe. T-shirts, etc. This way you’ll end up with a typical load instead of overload.

Photo copy the parts of the guidebook for the areas you’re going to. You can throw them away as you travel.

If you really need to, you can mail one or two packages back. Check with the Post Office on this for pricing.

It all depends on the money available.