[drunner]

How does it make sense? If I buy a book I'm entitled to rip out pages and black marker words. What's the difference to removing text or images of my choice while viewing a website?

[sneak]

It’s an unauthorized modification (and production of a derivative work) of a copyrighted work.

[slightwinder]

Which is not illegal for personal usage. You are just not allowed to share it, or even resell it. And even this has special cases.

[sterlind]

it's perfectly legal to modify any copyrighted work. it's only illegal for you to distribute copies.

so it should be legal to install an ad block plugin, but not legal to run an ad-stripping proxy.

[trenchpilgrim]

Which is perfectly legal to make under existing law.

[NoMoreNicksLeft]

Depends on what the license says in the first page of the book. It may actually disallow you ripping out pages. You don't own the book, you merely paid for a limited license to read it per the instructions provided in the license agreement. Anything else would be immoral.

[3036e4]

No, that is not how copyright works, at least not in this country, but probably not in many countries. You buy a book, not a license. Copyright luckily isn't an unlimited right to dictate exactly how a work is used.

Ebooks sadly are different. I only buy DRM-free ebooks that grant me rights similar to what always exists for printed books, but that sadly limits what ebooks I can buy quite significantly.

[trenchpilgrim]

This is not true - you have received a property right to the copy of the content and can legally alter or destroy it. A license in the book cannot override your property right.

You may encounter issues if you attempt to distribute the altered copy, but that's not at issue here.

[mnw21cam]

No, you absolutely own the book, but you have a licence for the information in it.

[ballenf]

Wouldn't the first sale doctrine override such terms in most cases?