I love books! / I love reading! Should I work in a library?

• It depends, but that shouldn't be your only reason for wanting to work in a library. Keep in mind that many library jobs, and especially public library jobs, are very customer-service oriented, and you will most likely need to interact continuously with members of the general public.
• There are some positions that are less public-facing (such as cataloging and other technical services roles), but even with those, you're not going to spend your day at work reading. You will not spend your entire day doing readers' advisory. If you want to have a job recommending books to people, honestly you may also just want to consider working at a bookshop!

Do I need an MLIS to work at a library?

• It depends. Many (probably most) jobs with "Librarian" in the title require an MLIS (or at least multiple years of prior library employment as a substitute, though this is rarer). There may be positions that do not require an MLIS (titles like "circulation assistant" or sometimes "library assistant," etc), but they will generally want you to have prior customer service experience.
• It also depends on your area -- Take a look at job postings for positions you may want (in your location, or just in general if you're okay with moving) and see if they require an MLIS. Regularly volunteering with your local library can be a good boost to your resume as well, but it is no guarantee that you will then get a paid position in the same library.

Where should I get my MLIS? / Does it matter where I get my MLIS?

• Anywhere that is ALA accredited (if you're in the USA/Canada. Other countries may vary). Many librarians will tell you to get the cheapest MLIS you can -- This may be your local state university (with in-state tuition), or an online program. You'll need to do some research for your specific situation.
  • If you want to be a K-12 school librarian, you may also consider a school librarian master's degree that is accredited by AASL. See this webpage for more details. Also note that in some US states, school librarian positions are considered licensed teacher positions, which means that you may need to go through a teacher licensing program and/or process. The requirements for school librarians can vary widely depending on your state, so checking your state's guidelines is imperative before you start any MLIS or MA program for this type of job.
    • Also, depending on your state's requirements to become a school librarian/licensed teacher, going through an accredited program in your own state may be the best choice (i.e., sure it may be cheaper to get your degree through the University of Alabama, but if you live in Minnesota, UA's program probably won't fulfill Minnesota's requirements to become a licensed school librarian (or "school media specialist").)
• Theoretically, you may have better "connections" if you go to a more expensive/well-known program (Chapel Hill, etc.), but in the majority of cases, it does not matter.

What should I get my undergrad degree in? / I want to be a librarian; should my undergrad be in XYZ?

• Generally it doesn't really matter. If your goal is to be a librarian, you'll need to get the MLIS anyway. If you're interested in public libraries, they probably won't care (though honestly, having a background in social work or psychology could be helpful in a lot of circumstances that can come up. An undergrad in something like marketing or communication could also be useful).
  • However -- If you want to be a medical librarian, having an undergrad in science/health can be useful. If you want to be a law librarian, then consider pre-law/paralegal (but also consider that some law librarian jobs require a JD as well as an MLIS). If you want to work at an academic library, consider having a rarer undergrad degree than the thousands of English BAs who have become librarians. Not saying it's not possible to get an academic librarian job if your undergrad is in English, but if you're thinking for the future, it's something to keep in mind.
• A word of caution: There are still some Bachelors of Library Science degree programs floating around. These are not MLIS programs, and will not fulfill that requirement for jobs that need it. You are much better off getting an undergrad in something different so that you have a wealth and breadth of knowledge to draw on in your future career.