The Mother Tongue has 279 pages.
Yes it is, tongue and mother tongue as a synonym.
A person's 'mother tongue' is the main language that they spoke when they were growing up. Usually this will be the language which they used with their mother (which explains the name): but obviously there are exceptions to this (if your mother was a Bangladeshi immigrant who married a mid-Westerner, and you grew up in Boise, then your mother tongue is probably American English - though you might still speak some Bengali with your mother). Recent language research suggests that the main language for most people is the language they speak with their childhood friends, not the language they speak at home: so 'mother tongue' may be a misnomer. It's still a useful idea though: and one that most people understand. Your mother tongue is your first language, the language you are most at ease in , the language in your dreams.
Someone who is bilingual knows two languages. The "mother tongue" would be the original, first language that the person learned. Usually the same language that is spoken in the region... but not always. There is not always a mother tongue. If a child grows up bilingual... two languages are spoken by the parents, and the child learns two languages from day one... that would be a case where "mother tongue" might not apply to the idea of bilingualism.
Depending on what you mean by "first language", there may be no difference. For most people it implies the language you learned first, which is your mother tongue. But for some it might mean "the language you are most fluent in or use most often" which might not be your mother tongue, if, for example, you emigrated at an early age.
English are used in many parts of the world even their mother tongue is not English. English is therefore a common language used internationally.
The Double Tongue has 160 pages.
Native Tongue - Carl Hiaasen novel - has 325 pages.
Spanish is the mother tongue but many do speak English.
Mother Warriors has 304 pages.
A Mother's Gift has 240 pages.
For Love of Mother-Not has 256 pages.
Mother London has 496 pages.
Mother of Storms has 432 pages.
"The Mother Hunt" by Rex Stout has 224 pages.
Native Tongue - Suzette Haden Elgin novel - has 320 pages.
What My Mother Doesn't Know has 272 pages.
Being a Green Mother has 313 pages.