Translation:I would read a book, but I cannot.
Thanks! I'm still confused about this sentence, though - does this imply that the speaker is illiterate, or is "nie mogę" more ambiguous (maybe he was lazy, maybe he ran out of time, maybe he lost the book)? I would think "nie mogłam" would be the ambiguous or more normal way to say it, but I am probably WAY overthinking things. :)
"Nie mogę" refers to the present. "Nie mogłam (she)" or "nie mogłem (he)" refers to the past.
As you were thinking "nie mogę" could be ambiguous, however in this context it means way, way more "I can't do this because I am busy" than "I can't do this because I can't read".
Other context, where "nie mogę" could be more directly translated is "Nie mogę tego przeczytać" (I can't read this - either because I can't read or I can't see the letter or I'm busy).
As mihxal said, if you don't possess the skill, you should say: "Nie umiem czytać" or "Nie potrafię czytać"
Hope this is not too fuzzy :P
Doesn't the verb "przeczytać" imply completion? Shouldn't an acceptable translation to this sentence be, "I would finish reading a/the book, but I cannot."?
What is the difference between "czytałabym książkę, ale nie mogę" and "przeczytałabym książkę, ale nie mogę"?
"Would have done" equates to Past Conditional in Romance languages. As far as I can see Polish doesn't distinguish between Present and Past Conditional forms, so perhaps it is possible here, but not, I think, in connection with "I can't".
It can only refer to the past, and doesn't really go with a verb in the Present Simple:
"I would have read the book, but I've been too busy lately"
"I would have read the book last week, but just didn't have the time"
But here "nie mogę" suggests we're talking about the present, so it would simply be "I would read". And this already has all the sense of completion we need.
As far as the English is concerned, "would read" means that sometime in the future, a future that starts right now, I would start to read this book, with the intention of finishing it.
"I would be reading" means that if it had been possible I would have already started reading and been in the process of reading now. It is often used in what is known in the trade as a Mixed Conditional:
"I would be reading it at this moment if you hadn't borrowed it and lost it"
When we say "I would read the book", it already has a sense of completion: when we start to read a book we generally intend to finish it. And if we didn't intend to complete it, we'd use a different verb, like "look at", for example.
On the other hand, "finish reading the book" only applies to the final process of reading a book, not reading the whole book. We'd never say it before we'd started reading.
For example, I have a book of 500 pages. I have already read up to Page 400, but for some reason stopped. Then I might talk of finishing it. But I'm pretty sure that in that case Polish would be using something like "skończyć". So I'm afraid I don't think it would really be a valid translation here.