A lot of these subtle differences just take time to become accustomed to, to really internalize how native speakers use them (and different regions might have different usages, so keep that in mind!)
Yes, but it's more "some people", as in the plural of "someone". It seems that "alguno" is meant to show indeterminate identity, as in "someone", "anyone", "somewhere", etc. The use of "algunos" here, I would think, emphasizes not the indeterminate number of the books, but their indeterminate identities. "Unos", on the other hand, emphasized the small but indeterminate number. It's a subtle distinction that's not so easy to make in English.
Pocos means few or little. A few would have to have some quantifier like unos pocos which would turn it into an approximation.
'I have few' is closer to 'I don not have many'. Glass half empty/something missing or lacking.
'I have a few' is closer to 'I have some quantity or amount that is more than two, but counting them out is inconvenient or unnecessary'. Approximate amount or generalization.
I thought alguna and alguno were always used in singular form, without the -s? (For example, in the previous question, where Duo used the phrase "alugna pregunta" to mean "some questions"). Can someone please explain when its okay to add the -s and when you should use just "alguno/alguna"? Gracias
"Several" is defined as "a few". The two words are synonymous. To say ,"this English word equals this foreign word and its English synonym equals this different foreign word" is absurd. If their meanings are the same, they are interchangeable. I understand that covering every nuance would be arduous, but I grow weary of trying to guess exactly which words will be accepted...
Okay, when we did "?Tienes alguna pregunta? we were told that alguna is always singular and has a singular noun it is describing. Now, I'm confused because in "Ella tiene algunos libros." we do indeed have a plural form of alguna with a plural noun! So, what's up? Is there actually anything inappropriate about "?Tienes algunas preguntas?"